Method of producing polyethylene and polyethylene thereof

ABSTRACT

A system and method of producing polyethylene, including: polymerizing ethylene in presence of a catalyst system in a reactor to form polyethylene, wherein the catalyst system includes a first catalyst and a second catalyst; and adjusting reactor conditions and an amount of the second catalyst fed to the reactor to control melt index (MI), density, and melt flow ratio (MFR) of the polyethylene.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplications having the following serial numbers: Ser. No. 61/938,466,by Ching-Tai Lue et al., filed Feb. 11, 2014 (2014U002.PRV); Ser. No.61/938,472, by Ching-Tai Lue et al., filed Feb. 11, 2014 (2014U003.PRV);Ser. No. 61/981,291, by Francis C. Rix et al., filed Apr. 18, 2014(2014U010.PRV); Ser. No. 61/985,151, by Francis C. Rix et al., filedApr. 28, 2014 (2014U012.PRV); Ser. No. 62/032,383, by Sun-Chueh Kao etal., filed Aug. 1, 2014 (2014U018.PRV); Ser. No. 62/087,905, by FrancisC. Rix et al., filed Dec. 5, 2014 (2014U035.PRV); Ser. No. 62/088,196,by Daniel P. Zilker, Jr. et al., filed Dec. 5, 2014 (2014U036.PRV), Ser.No. 62/087,911, by Ching-Tai Lue et al., filed Dec. 5, 2014(2014U037.PRV), and Ser. No. 62/087,914, by Francis C. Rix et al., filedDec. 5, 2014 (2014U038.PRV), the disclosures of which are incorporatedby reference in their entireties.

BACKGROUND

Ethylene alpha-olefin (polyethylene) copolymers are typically producedin a low pressure reactor, utilizing, for example, solution, slurry, orgas phase polymerization processes. Polymerization takes place in thepresence of catalyst systems such as those employing, for example, aZiegler-Natta catalyst, a chromium based catalyst, a metallocenecatalyst, or combinations thereof.

A number of catalyst compositions containing single site, e.g.,metallocene, catalysts have been used to prepare polyethylenecopolymers, producing relatively homogeneous copolymers at goodpolymerization rates. In contrast to traditional Ziegler-Natta catalystcompositions, single site catalyst compositions, such as metallocenecatalysts, are catalytic compounds in which each catalyst moleculecontains one or only a few polymerization sites. Single site catalystsoften produce polyethylene copolymers that have a narrow molecularweight distribution. Although there are single site catalysts that canproduce broader molecular weight distributions, these catalysts oftenshow a narrowing of the molecular weight distribution (MWD) as thereaction temperature is increased, for example, to increase productionrates. Further, a single site catalyst will often incorporate comonomeramong the molecules of the polyethylene copolymer at a relativelyuniform rate.

The composition distribution (CD) of an ethylene alpha-olefin copolymerrefers to the distribution of comonomer, which form short chainbranches, among the molecules that compose the polyethylene polymer.When the amount of short chain branches varies among the polyethylenemolecules, the resin is said to have a “broad” composition distribution.When the amount of comonomer per 1000 carbons is similar among thepolyethylene molecules of different chain lengths, the compositiondistribution is said to be “narrow.” It is generally known in the artthat a polyolefin's MWD and CD will affect the different productattributes.

To reduce or to avoid certain trade-off among desirable attributes,bimodal polymers have become increasingly important in the polyolefinsindustry, with a variety of manufacturers offering products of thistype. Whereas older technology relied on two-reactor systems to generatesuch material, advances in catalyst design and supporting technologyhave allowed for the development of single-reactor bimetallic catalystsystems capable of producing bimodal polyethylene. These systems areattractive both from a cost perspective and ease of use.

SUMMARY

Certain aspects relate to a system and method of producing polyethylene,including polymerizing ethylene in the presence of a catalyst system ina reactor to form polyethylene, wherein the catalyst system includes afirst catalyst and a second catalyst. The techniques include adjustingreactor conditions and an amount of the second catalyst fed to thereactor to control melt index (MI), density, and melt flow ratio (MFR)of the polyethylene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative plot of molecular weight distribution ofpolyolefin polymerized with a two catalyst system in accordance withembodiments described herein.

FIG. 2 is a schematic of a gas-phase reactor system, showing theaddition of at least two catalysts, at least one of which is added as atrim catalyst in accordance with embodiments described herein.

FIGS. 3A and 3B are plots that illustrate the calculations used todetermine a CFC result in accordance with embodiments described herein.

FIG. 4 is a plot of (Mw1/Mw2) vs. (Tw1−Tw2) showing a region ofpolymers.

FIG. 5A is a diagrammatical representation of techniques for generatingtargets or recipes, and producing, some of the exemplary BOCD polymersof Table 1, those listed in Table 2a.

FIG. 5B is a diagrammatical representation of techniques for generatingtargets or recipes, and producing, some of the exemplary BOCD polymersof Table 1, those listed in Table 2b.

FIG. 6 is an exemplary method 600 for producing polyethylene includingpolyethylene having BOCD.

DETAILED DESCRIPTION

As discussed below for producing polyethylene, the catalyst trim ratio,the polymerization reactor temperature, and the polymerization reactorhydrogen and comonomer concentrations, may be varied to give a range ofMFR at a substantially constant polyethylene density and MI (I-2). Thetechniques may beneficially accommodate a broad range of MI's with agiven catalyst system. Moreover, in embodiments, MI control may besubstantially decoupled from MFR control. For a catalyst system fed tothe polymerization reactor, the polymer MI, MFR, density, and CD may becontrolled by varying reactor conditions such as temperature, hydrogenconcentration, and comonomer (e.g., 1-hexene, butene, etc.)concentration.

Embodiments of the present techniques are directed to catalyst systemsand control of the polymerization reactor conditions to polymerizeethylene and any comonomer to form polyethylene. With respect to thepolyethylene produced in the polymerization reactor, certain embodimentsaccommodate independent control of melt flow ratio (MFR) and compositionfrom melt index (MI) and density, or vice versa. Indeed, embodiments mayaddress MI and density from melt flow ratio (MFR) and the relationshipbetween (i.e., combination of) MWD and CD composition. The techniquesaddress inter-relationships among catalyst, polyolefin product, andpolyolefin product performance. As appreciated by the skilled artisanfor nomenclature, the MI without notation is 1-2, and the MFR is theratio of MI(I-21)/MI(I-2).

The properties and performance of the polyethylene may be advanced bythe combination of: (1) selecting and feeding a dual catalyst systemhaving a first catalyst trimmed with a second catalyst; and (2) varyingreactor conditions such as reactor temperature, comonomer concentration,hydrogen concentration, and so on. With regard to some embodiments ofthe catalyst system, the first catalyst is a high molecular weightcomponent and the second (trim) catalyst is a low molecular weightcomponent. In other words, the first catalyst may provide primarily fora high molecular-weight portion of the polyethylene, and the secondcatalyst may provide primarily for a low molecular-weight portion of thepolyethylene.

Thus, in some embodiments, a first catalyst such as metallocene HfP orbis(n-propylcyclopentadienyl) Hafnium dimethyl, shown as structure (I)below may be selected to produce a higher molecular weight component ofthe polymer. In examples, the first catalyst may be fed in a slurry tothe polymerization reactor. A second catalyst such as the metalloceneEthInd, or meso and rac entantiomers of di(1-ethylindenyl) zirconiumdimethyl, shown as structures (II-A) and (II-B) below, may be selectedto produce a low molecular weight component of the polymer. Some or allof the second catalyst may be fed as a trim catalyst into the catalystslurry having the first catalyst in route to the polymerization reactor.

Of course, other metallocene catalysts (or non-metallocene catalysts),as described herein, may be selected, and other catalyst systemconfigurations implemented. The particular metallocene catalystsselected may depend on the specified properties of the polymer and thedesired downstream applications of the formed polymer resins, such forfilm, rotation molding, injection molding, blow-molding applications,pipe applications, and so on. The catalysts selected may includecatalysts that facilitate good (high) or poor (low) incorporation ofcomonomer (e.g., 1-hexene) into the polyethylene, have a relatively highresponse to hydrogen concentration in the reactor or a relatively lowresponse to reactor hydrogen concentration, and so on.

By using structures such as EthInd as the second catalyst trimmedon-line at various ratios onto slurry feeding the first catalyst such asthe first metallocene catalyst HfP, along with varying reactorconditions including temperature, reaction-mixture componentconcentrations, and the like, beneficial polyethylene products may beformed. In an alternate example, a reverse trim is employed in that theLMW catalyst species EthInd is the first catalyst and the HMW catalystspecies HfP is the second catalyst or catalyst trim. It should also benoted that for the various catalysts selected, some of the secondcatalyst may be initially co-deposited with the first catalyst on acommon support, and the remaining amount of the second catalyst added astrim. Of course, again, other configurations of the catalyst system arecontemplated.

In certain embodiments as indicated, the amount of second catalyst fed(or the catalyst trim ratio), and the reactor conditions (e.g.,temperature and hydrogen concentration), may be varied to give a rangeof MFR while maintaining polyethylene density and MI (I-2). Theembodiments may advantageously accommodate a broad range of MI's withthe same catalyst system, e.g., the same dual catalyst system. Indeed,MI control may be substantially decoupled from MFR control. For acatalyst system fed to the polymerization reactor, the polymer MI, MFR,density and CD may be controlled by varying reactor conditions such asthe reactor mixture including operating temperature, hydrogenconcentration, and comonomer concentration in reaction mixture.

In the exemplary Table 1a below, example aspects of reactor control withrespect to polyethylene properties are indicated. For instance, thehydrogen/ethylene (H2/C2) weight ratio or mol ratio may be an adjustmentor control knob or a “primary” adjustment knob, for polyethylene MIadjustment. The comonomer/ethylene (C6/C2) weight ratio or mol ratio maybe an adjustment or control knob or a “primary” adjustment knob, forpolyethylene density. The reactor temperature and the weight or molratio of the two catalysts (or the catalyst trim ratio) may be anadjustment or control knobs for the polyethylene MFR. Other adjustmentand control points are considered. Moreover, a primary property may bespecified and controlled first. For example, the MFR may be selected asa primary property of the polymer, and a range of MFR values of thepolymer consider for a given catalyst system used to produce thepolymer. In that example approach with a range of MFR values as primary,other polymer properties such as MI and density may be fine-tuned.Further, the techniques for reactor control described herein includingthe factors considered in Table 1a may apply to (1) direct control ofthe reactor during the actual production of the polyethylene, (2)development of recipe targets for reactor conditions for variouscatalyst systems (and amounts) and polyethylene grades or products, (3)polyethylene product development, and so forth

TABLE 1a Reactor Control Temperature C6/C2 H2/C2 Catalyst ratio MI XDensity X MFR X X

Exemplary ranges of MFR include 20 to 40, 20 to 45, 20 to 50, 20 to 60,and so forth. Exemplary ranges of MI (grams/10 minutes) include 0.1 to 4(e.g., for film), 5 to 50 or 100 (e.g., for molding such as rotationaland/or injection molding), and so on. Exemplary ranges for densityinclude 0.915 to 0.935, 0.912 to 0.940, 0.910 to 0.945, and the like.

It should be noted that without intelligently tailoring for specificMWD×CD, polyethylene copolymers usually exhibit trade-off paradigmsamong the desirable attribute, e.g., improving stiffness at the expenseof toughness or improving processability at the expense of toughness.Control of these properties may be obtained for the most part by thechoice of the catalyst system. Thus, the catalyst design is importantfor producing polymers that are attractive from a commercial standpoint.Because of the improved physical properties of polymers with thespecially tailored MWD×CD beneficial for commercially desirableproducts, embodiments herein address the need for controlled techniquesfor forming polyethylene copolymers having a specific MWD×CD.

In examples, sets of reactor conditions for making narrow MFR (low 20s)and broad MFR (high 20s) products with a single catalyst such as 100%HfP may be identified and implemented. For instance, reactor temperaturemay be used as a primary control variable for MFR adjustment with the100% HfP. Subsequently, at the chosen reactor temperature for a startingMFR, a trim-catalyst level may be added to further increase MFR until apre-set MFR range is reached. The component concentrations in thepolymerization mixture, such as hydrogen and comonomer (e.g., 1-hexene)concentrations, may be adjusted for specific MI and density targets ofthe polyethylene at the given MFR range. The amount of trim catalyst andreactor concentration adjustments may be repeated for various levels ofMFR range and specific MI and density targets. In a particular example,a polyethylene polymer having a MI of about 1.0 dg/min and a density ofabout 0.918 g/cm3 may be produced as a tie point for each MFR level.Such may be beneficial in identifying catalyst-product-performanceinter-relationships. Moreover, at each MFR level, additional grades forparticular market interests may be noted.

Embodiments demonstrate a novel technology to independently control apolyethylene product's MFR and/or MWD×CD composition from its MI anddensity in a single reactor environment. Consequently, some polyethyleneproducts may have a wide range of MWD×CD compositions and productattribute combinations. In examples, some of the polyethylene polymersmay have the same or similar nominal MI and density but different MFRand MWD×CD. Other polyethylene polymers in the examples have the same orsimilar nominal MI (I-2), density, and MFR but are different in MWD×CD.In some of the examples, the MI may range from 0.1 to 5.0 dg/min, 0.5 to1.0 dg/min, and other ranges, and the density may range from 0.912 to0.940 g/cm3, 0.916 to 0.926 g/cm3, and other ranges.

While the discussion herein may focus on multiple catalysts on acatalyst support and introduced to a polymerization reactor, the presentcatalysts may be applied in a variety of configurations. For example,the catalysts may be applied separately in a single-reactor ormultiple-reactor polymerization systems. The multiple catalysts may beapplied on a common support to a given reactor, applied via differentsupports, and/or utilized in reactor systems having a singlepolymerization reactor or more than one polymerization reactor, and soforth. The discussion now turns to embodiments related to multiplecatalysts, e.g., a first catalyst and a second catalyst, impregnated ona catalyst support for polymerization of monomer into a polymer.

A catalyst support impregnated with multiple catalysts may be used toform polymeric materials with improved balance of properties, such asstiffness, toughness, processibility, and environmental stress crackresistance. Such a balance of properties can be achieved, for example,by controlling the amounts and types of catalysts present on thesupport. Selection of the catalysts and ratios may adjust the combinedmolecular weight distribution (MWD) of the polymer produced. The MWD canbe controlled by combining catalysts giving the desired weight averagemolecular weight (Mw) and individual molecular weight distributions ofthe produced polymer. For example, the typical MWD for linearmetallocene polymers is 2.5 to 3.5. Blend studies indicate it would bedesirable to broaden this distribution by employing mixtures ofcatalysts that each provides different average molecular weights. Theratio of the Mw for a low molecular weight component and a highmolecular weight component would be between 1:1 and 1:10, or about 1:2and 1:5. Again, when a support is impregnated with multiple catalysts,new polymeric materials with improved balance of stiffness, toughnessand processability can be achieved, e.g., by controlling the amounts andtypes of catalysts present on the support. Appropriate selection of thecatalysts and ratios may be used to adjust the MWD, short chain branchdistribution (SCBD), and long-chain branch distribution (LCBD) of thepolymer, for example, to provide a polymer with a broad orthogonalcomposition distribution (BOCD). The MWD, SCBD, and LCBDs would becontrolled by combining catalysts with the appropriate weight averagemolecular weight (Mw), comonomer incorporation, and long chain branching(LCB) formation under the conditions of the polymerization. Polymershaving a broad orthogonal composition distribution (BOCD) in which thecomonomer is incorporated preferentially in the high molecular weightchains can lead to improved physical properties, for example, stiffness,toughness, processability, and environmental stress crack resistance(ESCR), among others. Because of the improved physical properties ofpolymers with orthogonal composition distributions needed forcommercially desirable products, controlled techniques for formingpolyethylene copolymers having a broad orthogonal compositiondistribution may be beneficial.

A number of catalyst compositions containing single site, e.g.,metallocene, catalysts have been used to prepare polyethylenecopolymers, producing relatively homogeneous copolymers at goodpolymerization rates. In contrast to traditional Ziegler-Natta catalystcompositions, single site catalyst compositions, such as metallocenecatalysts, are catalytic compounds in which each catalyst moleculecontains one or only a few polymerization sites. Single site catalystsoften produce polyethylene copolymers that have a narrow molecularweight distribution. Although there are single site catalysts that canproduce broader molecular weight distributions, these catalysts oftenshow a narrowing of the molecular weight distribution as the reactiontemperature is increased, for example, to increase production rates.Further, a single site catalyst will often incorporate comonomer amongthe molecules of the polyethylene copolymer at a relatively uniformrate. The molecular weight distribution (MWD) and the amount ofcomonomer incorporation can be used to determine a SCBD. For an ethylenealpha-olefin copolymer, short chain branching (SCB) on a polymer chainis typically created through comonomer incorporation duringpolymerization. Short chain branch distribution (SCBD) refers to thedistribution of short chain branches within a molecule or amongdifferent molecules that comprise the polyethylene polymer. When theamount of SCB varies among the polyethylene molecules, the resin is saidto have a “broad” SCBD. When the amount of SCB is similar among thepolyethylene molecules of different chain lengths, the SCBD is said tobe “narrow”. SCBD is known to influence the properties of copolymers,for example, stiffness, toughness, extractable content, environmentalstress crack resistance, and heat sealing, among other properties. SCBDof a polyolefin may be readily measured by methods known in the art, forexample, Temperature Raising Elution Fractionation (TREF) orCrystallization Analysis Fractionation (CRYSTAF). A polyolefin's MWD andSCBD is largely dictated by the type of catalyst used and is ofteninvariable for a given catalyst system. Ziegler-Natta catalysts andchromium based catalysts produce polymers with broad SCBD, whereasmetallocene catalysts normally produce polymers with narrow SCBD. It hasbeen long observed in the industry that there are trade-off paradigmsamong the different product attributes; most noticeably among stiffness,toughness, and processability (S/T/P). Since the introduction ofmetallocene in 1990s, some of such paradigms have been relaxedsignificantly with careful manipulations of molecular structure andcomposition in the product.

Employing multiple pre-catalysts that are co-supported on a singlesupport mixed with an activator, such as a silica methylaluminoxane(SMAO), can provide a cost advantage by making the product in onereactor instead of multiple reactors. Further, using a single supportalso facilitates intimate mixing of the polymers and offers improvedoperability relative to preparing a mixture of polymers of different Mwand density independently from multiple catalysts in a single reactor.As used herein, a pre-catalyst is a catalyst compound prior to exposureto activator. The catalysts can be co-supported during a singleoperation, or may be used in a trim operation, in which one or moreadditional catalysts are added to catalysts that are supported.

The density of a polyethylene copolymer provides an indication of theincorporation of comonomer into a polymer, with lower densitiesindicating higher incorporation. The difference in the densities of thelow molecular weight (LMW) component and the high molecular weight (HMW)component would preferably be greater than about 0.02, or greater thanabout 0.04, with the HMW component having a lower density than the LMWcomponent. These factors can be adjusted by controlling the MWD andSCBD, which, in turn, can be adjusted by changing the relative amount ofthe two pre-catalysts on the support. This may be adjusted during theformation of the pre-catalysts, for example, by supporting two catalystson a single support. In some embodiments, the relative amounts of thepre-catalysts can be adjusted by adding one of the components to acatalyst mixture en-route to the reactor in a process termed “trim.”Feedback of polymer property data can be used to control the amount ofcatalyst addition. Metallocenes (MCNs) are known to trim well with othercatalysts.

Further, a variety of polymers with different MWD, SCBD, and LCBD may beprepared from a limited number of catalysts. To do so, the pre-catalystsshould trim well onto activator supports. Two parameters that benefitthis are solubility in alkane solvents and rapid supportation on thecatalyst slurry en-route to the reactor. This favors the use of MCNs toachieve controlled MWD, SCBD, and LCBD. Techniques for selectingcatalysts that can be used to generate targeted molecular weightcompositions, including BOCD polymer systems, may be employed.

FIG. 1 is a plot 100 of molecular weight distributions for a twocatalyst system that includes a first catalyst that is a metallocenecatalyst or a non-metallocene catalyst, and a second catalyst that isanother metallocene, in accordance with embodiments described herein. Inthe plot 100, the x-axis 102 represents the log of the molecular weight,and the y-axis 104 represents the molecular weight distribution, i.e.,the amount of each molecular weight that is present. Each of thecatalysts can be selected to contribute a certain molecular weightcomponent. For example, a metallocene catalyst, such as structure (II-A)or structure (II-B) may be selected to produce a low molecular weightcomponent 106. Another metallocene, such as the catalyst shown instructure (I), or a non-metallocene, may be selected to produce a highermolecular weight component 108. The individual molecular weightcomponents form a single molecular weight distribution (MWD) 110 for thepolymer. Other metallocene catalysts, as described herein, may beselected. The particular metallocene catalysts selected may depend onthe desired downstream applications of the formed polymer resins, suchfor film, blow-molding applications, pipe applications, and so forth.

Generally, the mixed catalyst system provides a polymer with a mix ofbeneficial properties as a result of a carefully tailored combination ofmolecular weight distribution and the composition distribution. Theability to control the molecular weight distribution (MWD) and thecomposition distribution (CD) of the system is typically vital indetermining the processibility and strength of the resultant polymer.

These factors can be adjusted by controlling the MWD, which, in turn,can be adjusted by changing the relative amount of the combination ofpre-catalysts on the support. This may be adjusted during the formationof the pre-catalysts, for example, by supporting the three, or more,catalysts on a single support. In some embodiments, the relative amountsof the pre-catalysts can be adjusted by adding one of the components astrim to a catalyst mixture en-route to the reactor. Feedback of polymerproperty data can be used to control the amount of catalyst addition.

In sum, certain embodiments provide a polymerization system, method, andcatalyst system for producing polyethylene. The techniques includepolymerizing ethylene in the presence of a catalyst system in a reactorto form the polyethylene, wherein the catalyst system has a firstcatalyst such as metallocene catalyst, and a second catalyst such asanother metallocene catalyst or a non-metallocene catalyst. The reactorconditions and an amount of the second catalyst (or ratio of secondcatalyst to first catalyst) fed to the reactor may be adjusted tocontrol melt index (MI) (I-2) and density of the polyethylene based on atarget melt flow ratio (MFR) (I-21/I-2) and a desired combination of MWDand CD. The reactor conditions adjusted may be operating temperature ofthe reactor, a comonomer concentration and/or hydrogen concentration inthe polymerization mixture in the reactor, and the like. The reactantconcentrations may be adjusted to meet a MI target and/or density targetof the polyethylene, for example, at a given MFR range of thepolyethylene. In examples, the MI (I-2) of the polyethylene is in arange from 0.5 to 1.0 dg/min, and the density of the polyethylene is ina range from 0.916 to 0.926 g/cm3

In some embodiments, the first catalyst includes the metallocenecatalyst HfP, and the second catalyst is the metallocene Eth-Ind.Further, the catalyst system may be a common-supported catalyst system.Moreover, the second catalyst may be added as a trim catalyst to aslurry having the first catalyst fed the reactor. The first catalyst andthe second catalyst may be impregnated on a single support. Furthermore,in certain embodiments, the first catalyst promotes polymerization ofthe ethylene into a high molecular-weight portion of the polyethylene,and the second catalyst promotes polymerization of the ethylene into alow molecular-weight portion of the polyethylene. Again, an amount ofthe second catalyst fed (or the catalyst trim ratio) to thepolymerization reactor may be adjusted along with reactor conditions tocontrol polyolefin properties at a given MFR, for instance.

Other embodiments provide for a system and method of producingpolyethylene, including: polymerizing ethylene in presence of a catalystsystem in a reactor to form polyethylene, wherein the catalyst systemcomprises a first catalyst and a second catalyst; and adjusting reactortemperature, reactor hydrogen concentration, and an amount of the secondcatalyst fed to the reactor, to give a range of melt flow ratio (MFR) ofthe polyethylene while maintaining density and melt index (MI) of thepolyethylene. An initial amount of the second catalyst may beco-deposited with first catalyst prior to being fed to the reactor. Theadjusted amount of the second catalyst fed to the reactor may be thecatalyst trim ratio. In certain embodiments, the first catalyst promotespolymerization of the ethylene into a high molecular-weight portion ofthe polyethylene, and wherein the second catalyst promotespolymerization of the ethylene into a low molecular-weight portion ofthe polyethylene. In some embodiments, control of MI is substantiallydecoupled from control of MFR. In particular embodiments, the reactorhydrogen concentration as a ratio of hydrogen to ethylene in the reactoris a primary control variable for MI, a ratio of comonomer (e.g.,1-hexene) to ethylene in the reactor is a primary control variable forthe density, and the reactor temperature and the amount of the secondcatalyst fed to the reactor as a catalyst trim ratio are primary controlvariables of the MFR. In examples, the MFR is in the range of 20 to 45,the density is in the range of 0.912 to 0.940, and the MI is in therange of 0.1 dg/10 min to 100 dg/10 min.

Yet other embodiments provide for a system and method of producingpolyethylene, including: polymerizing ethylene in presence of a catalystsystem in a reactor to form polyethylene, wherein the catalyst systemcomprises a first catalyst and a second catalyst; and adjusting reactorconditions and an amount of the second catalyst fed to the reactor, toaccommodate a range of melt index (MI).

Various catalyst systems and components may be used to generate thepolymers and molecular weight compositions disclosed. These arediscussed in the sections to follow. The first section discussescatalyst compounds that can be used in embodiments, including the firstmetallocene and the second metallocene catalysts, among others. Thesecond section discusses generating catalyst slurries that may be usedfor implementing the techniques described. The third section discussessupports that may be used. The fourth section discusses catalystactivators that may be used. The fifth section discusses the catalystcomponent solutions that may be used to add additional catalysts in trimsystems. Gas phase polymerizations may use static control or continuityagents, which are discussed in the fifth section. A gas-phasepolymerization reactor with a trim feed system is discussed in the sixthsection. The use of the catalyst composition to control productproperties is discussed in a sixth section and an exemplarypolymerization process is discussed in the seventh section. Examples ofthe implementation of the procedures discussed in incorporated into aneighth section.

Catalyst Compounds Metallocene Catalyst Compounds

Metallocene catalyst compounds can include “half sandwich” and/or “fullsandwich” compounds having one or more Cp ligands (cyclopentadienyl andligands isolobal to cyclopentadienyl) bound to at least one Group 3 toGroup 12 metal atom, and one or more leaving group(s) bound to the atleast one metal atom. As used herein, all reference to the PeriodicTable of the Elements and groups thereof is to the NEW NOTATIONpublished in HAWLEY'S CONDENSED CHEMICAL DICTIONARY, Thirteenth Edition,John Wiley & Sons, Inc., (1997) (reproduced there with permission fromIUPAC), unless reference is made to the Previous IUPAC form noted withRoman numerals (also appearing in the same), or unless otherwise noted.

The Cp ligands are one or more rings or ring system(s), at least aportion of which includes π-bonded systems, such as cycloalkadienylligands and heterocyclic analogues. The ring(s) or ring system(s)typically include atoms selected from the group consisting of Groups 13to 16 atoms, and, in a particular exemplary embodiment, the atoms thatmake up the Cp ligands are selected from the group consisting of carbon,nitrogen, oxygen, silicon, sulfur, phosphorous, germanium, boron,aluminum, and combinations thereof, where carbon makes up at least 50%of the ring members. In a more particular exemplary embodiment, the Cpligand(s) are selected from the group consisting of substituted andunsubstituted cyclopentadienyl ligands and ligands isolobal tocyclopentadienyl, non-limiting examples of which includecyclopentadienyl, indenyl, fluorenyl and other structures. Furthernon-limiting examples of such ligands include cyclopentadienyl,cyclopentaphenanthreneyl, indenyl, benzindenyl, fluorenyl,octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene,phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl,8-H-cyclopent[a]acenaphthylenyl, 7-H-dibenzofluorenyl,indeno[1,2-9]anthrene, thiophenoindenyl, thiophenofluorenyl,hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or “H4Ind”), substituted versions thereof (as discussed and described in moredetail below), and heterocyclic versions thereof.

The metal atom “M” of the metallocene catalyst compound can be selectedfrom the group consisting of Groups 3 through 12 atoms and lanthanideGroup atoms in one exemplary embodiment; and selected from the groupconsisting of Groups 3 through 10 atoms in a more particular exemplaryembodiment; and selected from the group consisting of Sc, Ti, Zr, Hf, V,Nb, Ta, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, and Ni in yet a more particularexemplary embodiment; and selected from the group consisting of Groups4, 5, and 6 atoms in yet a more particular exemplary embodiment; and Ti,Zr, Hf atoms in yet a more particular exemplary embodiment; and Zr inyet a more particular exemplary embodiment. The oxidation state of themetal atom “M” can range from 0 to +7 in one exemplary embodiment; andin a more particular exemplary embodiment, can be +1, +2, +3, +4, or +5;and in yet a more particular exemplary embodiment can be +2, +3 or +4.The groups bound to the metal atom “M” are such that the compoundsdescribed below in the formulas and structures are electrically neutral,unless otherwise indicated. The Cp ligand forms at least one chemicalbond with the metal atom M to form the “metallocene catalyst compound.”The Cp ligands are distinct from the leaving groups bound to thecatalyst compound in that they are not highly susceptible tosubstitution/abstraction reactions.

The one or more metallocene catalyst compounds can be represented by thestructure (VI):

CpACpBMXn,

in which M is as described above; each X is chemically bonded to M; eachCp group is chemically bonded to M; and n is 0 or an integer from 1 to4, and either 1 or 2 in a particular exemplary embodiment.

The ligands represented by CpA and CpB in structure (VI) can be the sameor different cyclopentadienyl ligands or ligands isolobal tocyclopentadienyl, either or both of which can contain heteroatoms andeither or both of which can be substituted by a group R. In at least onespecific embodiment, CpA and CpB are independently selected from thegroup consisting of cyclopentadienyl, indenyl, tetrahydroindenyl,fluorenyl, and substituted derivatives of each.

Independently, each CpA and CpB of structure (VI) can be unsubstitutedor substituted with any one or combination of substituent groups R.Non-limiting examples of substituent groups R as used in structure (VI)as well as ring substituents in structures discussed and describedbelow, include groups selected from the group consisting of hydrogenradicals, alkyls, alkenyls, alkynyls, cycloalkyls, aryls, acyls, aroyls,alkoxys, aryloxys, alkylthiols, dialkylamines, alkylamidos,alkoxycarbonyls, aryloxycarbonyls, carbomoyls, alkyl- anddialkyl-carbamoyls, acyloxys, acylaminos, aroylaminos, and combinationsthereof. More particular non-limiting examples of alkyl substituents Rassociated with structures (VI) through (XI) include methyl, ethyl,propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl, phenyl,methylphenyl, and tert-butylphenyl groups and the like, including alltheir isomers, for example, tertiary-butyl, isopropyl, and the like.Other possible radicals include substituted alkyls and aryls such as,for example, fluoromethyl, fluroethyl, difluroethyl, iodopropyl,bromohexyl, chlorobenzyl, hydrocarbyl substituted organometalloidradicals including trimethylsilyl, trimethylgermyl, methyldiethylsilyl,and the like, and halocarbyl-substituted organometalloid radicals,including tris(trifluoromethyl)silyl, methylbis(difluoromethyl)silyl,bromomethyldimethylgermyl and the like; and disubstituted boron radicalsincluding dimethylboron, for example; and disubstituted Group 15radicals including dimethylamine, dimethylphosphine, diphenylamine,methylphenylphosphine, as well as Group 16 radicals including methoxy,ethoxy, propoxy, phenoxy, methylsulfide and ethylsulfide. Othersubstituent groups R include, but are not limited to, olefins such asolefinically unsaturated substituents including vinyl-terminated ligandssuch as, for example, 3-butenyl, 2-propenyl, 5-hexenyl, and the like. Inone exemplary embodiment, at least two R groups (two adjacent R groupsin a particular exemplary embodiment) are joined to form a ringstructure having from 3 to 30 atoms selected from the group consistingof carbon, nitrogen, oxygen, phosphorous, silicon, germanium, aluminum,boron, and combinations thereof. Also, a substituent group R such as1-butanyl can form a bonding association to the element M.

Each leaving group, or X, in the structure (VI) above and for thestructures in (VII) through (IX) below is independently selected fromthe group consisting of: halogen ions, hydrides, C1 to C12 alkyls, C2 toC12 alkenyls, C6 to C12 aryls, C7 to C20 alkylaryls, C1 to C12 alkoxys,C6 to C16 aryloxys, C7 to C8 alkylaryloxys, C1 to C12 fluoroalkyls, C6to C12 fluoroaryls, and C1 to C12 heteroatom-containing hydrocarbons andsubstituted derivatives thereof, in a more particular exemplaryembodiment; hydride, halogen ions, C1 to C6 alkyls, C2 to C6 alkenyls,C7 to C18 alkylaryls, C1 to C6 alkoxys, C6 to C14 aryloxys, C7 to C16alkylaryloxys, C1 to C6 alkylcarboxylates, C1 to C6 fluorinatedalkylcarboxylates, C6 to C12 arylcarboxylates, C7 to C18alkylarylcarboxylates, C1 to C6 fluoroalkyls, C2 to C6 fluoroalkenyls,and C7 to C18 fluoroalkylaryls in yet a more particular exemplaryembodiment; hydride, chloride, fluoride, methyl, phenyl, phenoxy,benzoxy, tosyl, fluoromethyls and fluorophenyls, in yet a moreparticular exemplary embodiment; C1 to C12 alkyls, C2 to C12 alkenyls,C6 to C12 aryls, C7 to C20 alkylaryls, substituted C1 to C12 alkyls,substituted C6 to C12 aryls, substituted C7 to C20 alkylaryls and C1 toC12 heteroatom-containing alkyls, C1 to C12 heteroatom-containing aryls,and C1 to C12 heteroatom-containing alkylaryls, in yet a more particularexemplary embodiment; chloride, fluoride, C1 to C6 alkyls, C2 to C6alkenyls, C7 to C18 alkylaryls, halogenated C1 to C6 alkyls, halogenatedC2 to C6 alkenyls, and halogenated C7 to C18 alkylaryls, in yet a moreparticular exemplary embodiment; chloride, methyl, ethyl, propyl,phenyl, methylphenyl, dimethylphenyl, trimethylphenyl, fluoromethyls(mono-, di- and trifluoromethyls) and fluorophenyls (mono-, di-, tri-,tetra- and pentafluorophenyls), in yet a more particular exemplaryembodiment.

Other non-limiting examples of X groups include amides, amines,phosphines, ethers, carboxylates, dienes, hydrocarbon radicals havingfrom 1 to 20 carbon atoms, fluorinated hydrocarbon radicals (e.g., —C6F5(pentafluorophenyl)), fluorinated alkylcarboxylates (e.g., CF3C(O)O—),hydrides, halogen ions and combinations thereof. Other examples of Xligands include alkyl groups such as cyclobutyl, cyclohexyl, methyl,heptyl, tolyl, trifluoromethyl, tetramethylene, pentamethylene,methylidene, methyoxy, ethyoxy, propoxy, phenoxy, bis(N-methylanilide),dimethylamide, dimethylphosphide radicals and the like. In one exemplaryembodiment, two or more X's form a part of a fused ring or ring system.In at least one specific embodiment, X can be a leaving group selectedfrom the group consisting of chloride ions, bromide ions, C1 to C10alkyls, and C2 to C12 alkenyls, carboxylates, acetylacetonates, andalkoxides.

The metallocene catalyst compound includes those of structure (VI) whereCpA and CpB are bridged to each other by at least one bridging group,(A), such that the structure is represented by structure (VII):

CpA(A)CpBMXn.

These bridged compounds represented by structure (VII) are known as“bridged metallocenes.” The elements CpA, CpB, M, X and n in structure(VII) are as defined above for structure (VI); where each Cp ligand ischemically bonded to M, and (A) is chemically bonded to each Cp. Thebridging group (A) can include divalent hydrocarbon groups containing atleast one Group 13 to 16 atom, such as, but not limited to, at least oneof a carbon, oxygen, nitrogen, silicon, aluminum, boron, germanium, tinatom, and combinations thereof; where the heteroatom can also be C1 toC12 alkyl or aryl substituted to satisfy neutral valency. In at leastone specific embodiment, the bridging group (A) can also includesubstituent groups R as defined above (for structure (VI)) includinghalogen radicals and iron. In at least one specific embodiment, thebridging group (A) can be represented by C1 to C6 alkylenes, substitutedC1 to C6 alkylenes, oxygen, sulfur, R′2C═, R′2Si═, ═Si(R′)2Si(R′ 2)═,R′2Ge═, and R′P═, where “═” represents two chemical bonds, R′ isindependently selected from the group consisting of hydride,hydrocarbyl, substituted hydrocarbyl, halocarbyl, substitutedhalocarbyl, hydrocarbyl-substituted organometalloid,halocarbyl-substituted organometalloid, disubstituted boron,disubstituted Group 15 atoms, substituted Group 16 atoms, and halogenradical; and where two or more R′ can be joined to form a ring or ringsystem. In at least one specific embodiment, the bridged metallocenecatalyst compound of structure (VII) includes two or more bridginggroups (A). In one or more embodiments, (A) can be a divalent bridginggroup bound to both CpA and CpB selected from the group consisting ofdivalent C1 to C20 hydrocarbyls and C1 to C20 heteroatom containinghydrocarbonyls, where the heteroatom containing hydrocarbonyls includefrom one to three heteroatoms.

The bridging group (A) can include methylene, ethylene, ethylidene,propylidene, isopropylidene, diphenylmethylene, 1,2-dimethylethylene,1,2-diphenylethylene, 1,1,2,2-tetramethylethylene, dimethylsilyl,diethylsilyl, methyl-ethylsilyl, trifluoromethylbutylsilyl,bis(trifluoromethyl)silyl, di(n-butyl)silyl, di(n-propyl)silyl,di(i-propyl)silyl, di(n-hexyl)silyl, dicyclohexylsilyl, diphenylsilyl,cyclohexylphenylsilyl, t-butylcyclohexylsilyl, di(t-butylphenyl)silyl,di(p-tolyl)silyl and the corresponding moieties where the Si atom isreplaced by a Ge or a C atom; as well as dimethylsilyl, diethylsilyl,dimethylgermyl and diethylgermyl.

The bridging group (A) can also be cyclic, having, for example, 4 to 10ring members; in a more particular exemplary embodiment, bridging group(A) can have 5 to 7 ring members. The ring members can be selected fromthe elements mentioned above, and, in a particular embodiment, can beselected from one or more of B, C, Si, Ge, N, and O. Non-limitingexamples of ring structures which can be present as, or as part of, thebridging moiety are cyclobutylidene, cyclopentylidene, cyclohexylidene,cycloheptylidene, cyclooctylidene and the corresponding rings where oneor two carbon atoms are replaced by at least one of Si, Ge, N and O. Inone or more embodiments, one or two carbon atoms can be replaced by atleast one of Si and Ge. The bonding arrangement between the ring and theCp groups can be cis-, trans-, or a combination thereof.

The cyclic bridging groups (A) can be saturated or unsaturated and/orcan carry one or more substituents and/or can be fused to one or moreother ring structures. If present, the one or more substituents can be,in at least one specific embodiment, selected from the group consistingof hydrocarbyl (e.g., alkyl, such as methyl) and halogen (e.g., F, Cl).The one or more Cp groups to which the above cyclic bridging moietiescan optionally be fused can be saturated or unsaturated, and areselected from the group consisting of those having 4 to 10, moreparticularly 5, 6, or 7 ring members (selected from the group consistingof C, N, O, and S in a particular exemplary embodiment) such as, forexample, cyclopentyl, cyclohexyl and phenyl. Moreover, these ringstructures can themselves be fused such as, for example, in the case ofa naphthyl group. Moreover, these (optionally fused) ring structures cancarry one or more substituents. Illustrative, non-limiting examples ofthese substituents are hydrocarbyl (particularly alkyl) groups andhalogen atoms. The ligands CpA and CpB of structure (VI) and (VII) canbe different from each other. The ligands CpA and CpB of structure (VI)and (VII) can be the same. The metallocene catalyst compound can includebridged mono-ligand metallocene compounds (e.g., mono cyclopentadienylcatalyst components).

It is contemplated that the metallocene catalyst components discussedand described above include their structural or optical or enantiomericisomers (racemic mixture), and, in one exemplary embodiment, can be apure enantiomer. As used herein, a single, bridged, asymmetricallysubstituted metallocene catalyst compound having a racemic and/or mesoisomer does not, itself, constitute at least two different bridged,metallocene catalyst components.

The amount of the transition metal component of the one or moremetallocene catalyst compounds in the catalyst system can range from alow of about 0.2 wt. %, about 3 wt. %, about 0.5 wt. %, or about 0.7 wt.% to a high of about 1 wt. %, about 2 wt. %, about 2.5 wt. %, about 3wt. %, about 3.5 wt. %, or about 4 wt. %, based on the total weight ofthe catalyst system.

The metallocene catalyst compounds can include any combination of anyembodiment discussed and described herein. For example, the metallocenecatalyst compound can include, but is not limited to,bis(n-butylcyclopentadienyl) zirconium (CH3)2,bis(n-butylcyclopentadienyl) zirconium Cl2, bis(n-butylcyclopentadienyl)zirconium Cl2, (n-propylcyclopentadienyl, tetramethylcyclopentadienyl)zirconium Cl2, [(pentamethyphenylNCH2CH2)2NH]ZrBn2,[(pentamethylphenylNCH2CH2)2O]ZrBn2, or any combinations thereof. Othermetallocene catalyst compounds are contemplated.

Although the catalyst compounds may be written or shown with methyl-,chloro-, or phenyl-leaving groups attached to the central metal, it canbe understood that these groups may be different without changing thecatalyst involved. For example, each of these ligands may independentlybe a benzyl group (Bn), a methyl group (Me), a chloro group (Cl), afluoro group (F), or any number of other groups, including organicgroups, or heteroatom groups. Further, these ligands will change duringthe reaction, as a pre-catalyst is converted to the active catalyst forthe reaction.

Group 15 Atom and Non-Metallocene Catalyst Compounds

The catalyst system can include one or more Group 15 metal-containingcatalyst compounds. As used herein, these are termed non-metallocenecatalyst compounds. The Group 15 metal-containing compound generallyincludes a Group 3 to 14 metal atom, a Group 3 to 7, or a Group 4 to 6metal atom. In many embodiments, the Group 15 metal-containing compoundincludes a Group 4 metal atom bound to at least one leaving group andalso bound to at least two

Group 15 atoms, at least one of which is also bound to a Group 15 or 16atom through another group.

In one or more embodiments, at least one of the Group 15 atoms is alsobound to a Group 15 or 16 atom through another group which may be a C1to C20 hydrocarbon group, a heteroatom containing group, silicon,germanium, tin, lead, or phosphorus, wherein the Group 15 or 16 atom mayalso be bound to nothing or a hydrogen, a Group 14 atom containinggroup, a halogen, or a heteroatom containing group, and wherein each ofthe two Group 15 atoms are also bound to a cyclic group and canoptionally be bound to hydrogen, a halogen, a heteroatom or ahydrocarbyl group, or a heteroatom containing group.

The Group 15-containing metal compounds can be described moreparticularly with structures (VIII) or (IX):

where M is a Group 3 to 12 transition metal or a Group 13 or 14 maingroup metal, a Group 4, 5, or 6 metal. In many embodiments, M is a Group4 metal, such as zirconium, titanium, or hafnium. Each X isindependently a leaving group, such as an anionic leaving group. Theleaving group may include a hydrogen, a hydrocarbyl group, a heteroatom,a halogen, or an alkyl; y is 0 or 1 (when y is 0 group L′ is absent).The term ‘n’ is the oxidation state of M. In various embodiments, n is+3, +4, or +5. In many embodiments, n is +4. The term ‘m’ represents theformal charge of the YZL or the YZL′ ligand, and is 0, −1, −2 or −3 invarious embodiments. In many embodiments, m is −2. L is a Group 15 or 16element, such as nitrogen or oxygen; L′ is a Group 15 or 16 element orGroup 14 containing group, such as carbon, silicon or germanium. Y is aGroup 15 element, such as nitrogen or phosphorus. In many embodiments, Yis nitrogen. Z is a Group 15 element, such as nitrogen or phosphorus. Inmany embodiments, Z is nitrogen. R1 and R2 are, independently, a C1 toC20 hydrocarbon group, a heteroatom containing group having up to twentycarbon atoms, silicon, germanium, tin, lead, or phosphorus. In manyembodiments, R1 and R2 are a C2 to C20 alkyl, aryl or aralkyl group,such as a linear, branched or cyclic C2 to C20 alkyl group, or a C2 toC6 hydrocarbon group, such as the X described with respect to structures(VI) and (VII) above. R1 and R2 may also be interconnected to eachother. R3 may be absent or may be a hydrocarbon group, a hydrogen, ahalogen, a heteroatom containing group. In many embodiments, R3 isabsent, for example, if L is an oxygen, or a hydrogen, or a linear,cyclic, or branched alkyl group having 1 to 20 carbon atoms. R4 and R5are independently an alkyl group, an aryl group, substituted aryl group,a cyclic alkyl group, a substituted cyclic alkyl group, a cyclic aralkylgroup, a substituted cyclic aralkyl group, or multiple ring system,often having up to 20 carbon atoms. In many embodiments, R4 and R5 havebetween 3 and 10 carbon atoms, or are a C1 to C20 hydrocarbon group, aC1 to C20 aryl group or a C1 to C20 aralkyl group, or a heteroatomcontaining group. R4 and R5 may be interconnected to each other. R6 andR7 are independently absent, hydrogen, an alkyl group, halogen,heteroatom, or a hydrocarbyl group, such as a linear, cyclic or branchedalkyl group having 1 to 20 carbon atoms. In many embodiments, R6 and R7are absent. R* may be absent, or may be a hydrogen, a Group 14 atomcontaining group, a halogen, or a heteroatom containing group.

By “formal charge of the YZL or YZL′ ligand,” it is meant the charge ofthe entire ligand absent the metal and the leaving groups X. By “R1 andR2 may also be interconnected” it is meant that R1 and R2 may bedirectly bound to each other or may be bound to each other through othergroups. By “R4 and R5 may also be interconnected” it is meant that R4and R5 may be directly bound to each other or may be bound to each otherthrough other groups. An alkyl group may be linear, branched alkylradicals, alkenyl radicals, alkynyl radicals, cycloalkyl radicals, arylradicals, acyl radicals, aroyl radicals, alkoxy radicals, aryloxyradicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonylradicals, aryloxycarbonyl radicals, carbomoyl radicals, alkyl- ordialkyl-carbamoyl radicals, acyloxy radicals, acylamino radicals,aroylamino radicals, straight, branched or cyclic, alkylene radicals, orcombination thereof. An aralkyl group is defined to be a substitutedaryl group.

In one or more embodiments, R4 and R5 are independently a grouprepresented by the following structure (X).

When R⁴ and R⁵ are as formula VII, R⁸ to R¹² are each independentlyhydrogen, a C₁ to C₄₀ alkyl group, a halide, a heteroatom, a heteroatomcontaining group containing up to 40 carbon atoms. In many embodiments,R⁸ to R¹² are a C₁ to C₂₀ linear or branched alkyl group, such as amethyl, ethyl, propyl, or butyl group. Any two of the R groups may forma cyclic group and/or a heterocyclic group. The cyclic groups may bearomatic. In one embodiment R⁹, R¹⁰ and R¹² are independently a methyl,ethyl, propyl, or butyl group (including all isomers). In anotherembodiment, R⁹, R¹⁰ and R¹² are methyl groups, and R⁸ and R¹¹ arehydrogen.

In one or more embodiments, R⁴ and R⁵ are both a group represented bythe following structure (XI).

When R4 and R5 follow structure (XI), M is a Group 4 metal, such aszirconium, titanium, or hafnium. In many embodiments, M is zirconium.Each of L, Y, and Z may be a nitrogen. Each of R1 and R2 may be—CH2—CH2—. R3 may be hydrogen, and R6 and R7 may be absent. The Group 15metal-containing catalyst compound can be represented by structure (IV).In formula IV, Ph represents phenyl.

Catalyst Forms

The catalyst system may include a catalyst component in a slurry, whichmay have an initial catalyst compound, and an added solution catalystcomponent that is added to the slurry. Generally, the first metallocenecatalyst will be supported in the initial slurry, depending onsolubility. However, in some embodiments, the initial catalyst componentslurry may have no catalysts. In this case, two or more solutioncatalysts may be added to the slurry to cause each to be supported.

Any number of combinations of catalyst components may be used inembodiments. For example, the catalyst component slurry can include anactivator and a support, or a supported activator. Further, the slurrycan include a catalyst compound in addition to the activator and thesupport. As noted, the catalyst compound in the slurry may be supported.

The slurry may include one or more activators and supports, and one morecatalyst compounds. For example, the slurry may include two or moreactivators (such as alumoxane and a modified alumoxane) and a catalystcompound, or the slurry may include a supported activator and more thanone catalyst compounds. In one embodiment, the slurry includes asupport, an activator, and two catalyst compounds. In another embodimentthe slurry includes a support, an activator and two different catalystcompounds, which may be added to the slurry separately or incombination. The slurry, containing silica and alumoxane, may becontacted with a catalyst compound, allowed to react, and thereafter theslurry is contacted with another catalyst compound, for example, in atrim system.

The molar ratio of metal in the activator to metal in the catalystcompound in the slurry may be 1000:1 to 0.5:1, 300:1 to 1:1, or 150:1 to1:1. The slurry can include a support material which may be any inertparticulate carrier material known in the art, including, but notlimited to, silica, fumed silica, alumina, clay, talc or other supportmaterials such as disclosed above. In one embodiment, the slurrycontains silica and an activator, such as methyl aluminoxane (“MAO”),modified methyl aluminoxane (“MMAO”), as discussed further below.

One or more diluents or carriers can be used to facilitate thecombination of any two or more components of the catalyst system in theslurry or in the trim catalyst solution. For example, the single sitecatalyst compound and the activator can be combined together in thepresence of toluene or another non-reactive hydrocarbon or hydrocarbonmixture to provide the catalyst mixture. In addition to toluene, othersuitable diluents can include, but are not limited to, ethylbenzene,xylene, pentane, hexane, heptane, octane, other hydrocarbons, or anycombination thereof. The support, either dry or mixed with toluene canthen be added to the catalyst mixture or the catalyst/activator mixturecan be added to the support.

The catalyst is not limited to a slurry arrangement, as a mixed catalystsystem may be made on a support and dried. The dried catalyst system canthen be fed to the reactor through a dry feed system.

Support

As used herein, the terms “support” and “carrier” are usedinterchangeably and refer to any support material, including a poroussupport material, such as talc, inorganic oxides, and inorganicchlorides. The one or more single site catalyst compounds of the slurrycan be supported on the same or separate supports together with theactivator, or the activator can be used in an unsupported form, or canbe deposited on a support different from the single site catalystcompounds, or any combination thereof. This may be accomplished by anytechnique commonly used in the art. There are various other methods inthe art for supporting a single site catalyst compound. For example, thesingle site catalyst compound can contain a polymer bound ligand. Thesingle site catalyst compounds of the slurry can be spray dried. Thesupport used with the single site catalyst compound can befunctionalized.

The support can be or include one or more inorganic oxides, for example,of Group 2, 3, 4, 5, 13, or 14 elements. The inorganic oxide caninclude, but is not limited to silica, alumina, titania, zirconia,boria, zinc oxide, magnesia, or any combination thereof. Illustrativecombinations of inorganic oxides can include, but are not limited to,alumina-silica, silica-titania, alumina-silica-titania,alumina-zirconia, alumina-titania, and the like. The support can be orinclude silica, alumina, or a combination thereof. In one embodimentdescribed herein, the support is silica.

Suitable commercially available silica supports can include, but are notlimited to, ES757, ES70, and ES70W available from PQ Corporation.Suitable commercially available silica-alumina supports can include, butare not limited to, SIRAL® 1, SIRAL® 5, SIRAL® 10, SIRAL® 20, SIRAL®28M, SIRAL® 30, and SIRAL® 40, available from SASOL®. Generally,catalysts supports comprising silica gels with activators, such asmethylaluminoxanes (MAOs), are used in the trim systems described, sincethese supports may function better for cosupporting solution carriedcatalysts.

Activator

As used herein, the term “activator” may refer to any compound orcombination of compounds, supported, or unsupported, which can activatea single site catalyst compound or component, such as by creating acationic species of the catalyst component. For example, this caninclude the abstraction of at least one leaving group (the “X” group inthe single site catalyst compounds described herein) from the metalcenter of the single site catalyst compound/component. The activator mayalso be referred to as a “co-catalyst”.

For example, the activator can include a Lewis acid or anon-coordinating ionic activator or ionizing activator, or any othercompound including Lewis bases, aluminum alkyls, and/orconventional-type co-catalysts. In addition to methylaluminoxane (“MAO”)and modified methylaluminoxane (“MMAO”) mentioned above, illustrativeactivators can include, but are not limited to, aluminoxane or modifiedaluminoxane, and/or ionizing compounds, neutral or ionic, such as tri(n-butyl)ammonium tetrakis(pentafluorophenyl)boron, atrisperfluorophenyl boron metalloid precursor, a trisperfluoronaphthylboron metalloid precursor, or any combinations thereof.

Aluminoxanes can be described as oligomeric aluminum compounds having—Al(R)—O— subunits, where R is an alkyl group. Examples of aluminoxanesinclude, but are not limited to, methylaluminoxane (“MAO”), modifiedmethylaluminoxane (“MMAO”), ethylaluminoxane, isobutylaluminoxane, or acombination thereof. Aluminoxanes can be produced by the hydrolysis ofthe respective trialkylaluminum compound. MMAO can be produced by thehydrolysis of trimethylaluminum and a higher trialkylaluminum, such astriisobutylaluminum. MMAOs are generally more soluble in aliphaticsolvents and more stable during storage. There are a variety of methodsfor preparing aluminoxane and modified aluminoxanes.

As noted above, one or more organo-aluminum compounds such as one ormore alkylaluminum compounds can be used in conjunction with thealuminoxanes. For example, alkylaluminum species that may be used arediethylaluminum ethoxide, diethylaluminum chloride, and/ordiisobutylaluminum hydride. Examples of trialkylaluminum compoundsinclude, but are not limited to, trimethylaluminum, triethylaluminum(“TEAL”), triisobutylaluminum (“TiBAl”), tri-n-hexylaluminum,tri-n-octylaluminum, tripropylaluminum, tributylaluminum, and the like.

Catalyst Component Solution

The catalyst component solution may include only a catalyst compound,such as a metallocene, or may include an activator in addition to thecatalyst compound. The catalyst solution used in the trim process can beprepared by dissolving the catalyst compound and optional activators ina liquid solvent. The liquid solvent may be an alkane, such as a C5 toC30 alkane, or a C5 to C10 alkane. Cyclic alkanes such as cyclohexaneand aromatic compounds such as toluene may also be used. In addition,mineral oil may be used as a solvent. The solution employed should beliquid under the conditions of polymerization and relatively inert. Inone embodiment, the liquid utilized in the catalyst compound solution isdifferent from the diluent used in the catalyst component slurry. Inanother embodiment, the liquid utilized in the catalyst compoundsolution is the same as the diluent used in the catalyst componentsolution.

If the catalyst solution includes both activator and catalyst compound,the ratio of metal in the activator to metal in the catalyst compound inthe solution may be 1000:1 to 0.5:1, 300:1 to 1:1, or 150:1 to 1:1. Invarious embodiments, the activator and catalyst compound are present inthe solution at up to about 90 wt. %, at up to about 50 wt. %, at up toabout 20 wt. %, preferably at up to about 10 wt. %, at up to about 5 wt.%, at less than 1 wt. %, or between 100 ppm and 1 wt. %, based upon theweight of the solvent and the activator or catalyst compound.

The catalyst component solution can comprises any one of the solublecatalyst compounds described in the catalyst section herein. As thecatalyst is dissolved in the solution, a higher solubility is desirable.Accordingly, the catalyst compound in the catalyst component solutionmay often include a metallocene, which may have higher solubility thanother catalysts.

In the polymerization process, described below, any of the abovedescribed catalyst component containing solutions may be combined withany of the catalyst component containing slurry/slurries describedabove. In addition, more than one catalyst component solution may beutilized.

Continuity Additive/Static Control Agent

In gas-phase polyethylene production processes, it may be desirable touse one or more static control agents to aid in regulating static levelsin the reactor. As used herein, a static control agent is a chemicalcomposition which, when introduced into a fluidized bed reactor, mayinfluence or drive the static charge (negatively, positively, or tozero) in the fluidized bed. The specific static control agent used maydepend upon the nature of the static charge, and the choice of staticcontrol agent may vary dependent upon the polymer being produced and thesingle site catalyst compounds being used.

Control agents such as aluminum stearate may be employed. The staticcontrol agent used may be selected for its ability to receive the staticcharge in the fluidized bed without adversely affecting productivity.Other suitable static control agents may also include aluminumdistearate, ethoxlated amines, and anti-static compositions such asthose provided by Innospec Inc. under the trade name OCTASTAT. Forexample, OCTASTAT 2000 is a mixture of a polysulfone copolymer, apolymeric polyamine, and oil-soluble sulfonic acid.

Any of the aforementioned control agents may be employed either alone orin combination as a control agent. For example, the carboxylate metalsalt may be combined with an amine containing control agent (e.g., acarboxylate metal salt with any family member belonging to the KEMAMINE®(available from Crompton Corporation) or ATMER® (available from ICIAmericas Inc.) family of products).

Other useful continuity additives include ethyleneimine additives usefulin embodiments disclosed herein may include polyethyleneimines havingthe following general formula:

—(CH₂—CH₂—NH)_(n)—,

in which n may be from about 10 to about 10,000. The polyethyleneiminesmay be linear, branched, or hyperbranched (e.g., forming dendritic orarborescent polymer structures). They can be a homopolymer or copolymerof ethyleneimine or mixtures thereof (referred to aspolyethyleneimine(s) hereafter). Although linear polymers represented bythe chemical formula —[CH2—CH2—NH]— may be used as thepolyethyleneimine, materials having primary, secondary, and tertiarybranches can also be used. Commercial polyethyleneimine can be acompound having branches of the ethyleneimine polymer.

Suitable polyethyleneimines are commercially available from BASFCorporation under the trade name Lupasol. These compounds can beprepared as a wide range of molecular weights and product activities.Examples of commercial polyethyleneimines sold by BASF suitable for usein the present invention include, but are not limited to, Lupasol FG andLupasol WF.

Another useful continuity additive can include a mixture of aluminumdistearate and an ethoxylated amine-type compound, e.g., IRGASTATAS-990, available from Huntsman (formerly Ciba Specialty Chemicals). Themixture of aluminum distearate and ethoxylated amine type compound canbe slurried in mineral oil e.g., Hydrobrite 380. For example, themixture of aluminum distearate and an ethoxylated amine type compoundcan be slurried in mineral oil to have total slurry concentration ofranging from about 5 wt. % to about 50 wt. % or about 10 wt. % to about40 wt. %, or about 15 wt. % to about 30 wt. %. Other static controlagents are applicable.

The continuity additive(s) or static control agent(s) may be added tothe reactor in an amount ranging from 0.05 to 200 ppm, based on theweight of all feeds to the reactor, excluding recycle. In someembodiments, the continuity additive may be added in an amount rangingfrom 2 to 100 ppm, or in an amount ranging from 4 to 50 ppm.

Gas Phase Polymerization Reactor

FIG. 2 is a schematic of a gas-phase reactor system 200, showing theaddition of at least two catalysts, at least one of which is added as atrim catalyst. The catalyst component slurry, preferably a mineral oilslurry including at least one support and at least one activator, atleast one supported activator, and optional catalyst compounds may beplaced in a vessel or catalyst pot (cat pot) 202. In one embodiment, thecat pot 202 is an agitated holding tank designed to keep the solidsconcentration homogenous. A catalyst component solution, prepared bymixing a solvent and at least one catalyst compound and/or activator, isplaced in another vessel, which can be termed a trim pot 204. Thecatalyst component slurry can then be combined in-line with the catalystcomponent solution to form a final catalyst composition. A nucleatingagent 206, such as silica, alumina, fumed silica or any otherparticulate matter may be added to the slurry and/or the solutionin-line or in the vessels 202 or 204. Similarly, additional activatorsor catalyst compounds may be added in-line. For example, a secondcatalyst slurry that includes a different catalyst may be introducedfrom a second cat pot. The two catalyst slurries may be used as thecatalyst system with or without the addition of a solution catalyst fromthe trim pot.

The catalyst component slurry and solution can be mixed in-line. Forexample, the solution and slurry may be mixed by utilizing a staticmixer 208 or an agitating vessel (not shown). The mixing of the catalystcomponent slurry and the catalyst component solution should be longenough to allow the catalyst compound in the catalyst component solutionto disperse in the catalyst component slurry such that the catalystcomponent, originally in the solution, migrates to the supportedactivator originally present in the slurry. The combination forms auniform dispersion of catalyst compounds on the supported activatorforming the catalyst composition. The length of time that the slurry andthe solution are contacted is typically up to about 220 minutes, such asabout 1 to about 60 minutes, about 5 to about 40 minutes, or about 10 toabout 30 minutes.

When combining the catalysts, the activator and the optional support oradditional co-catalysts, in the hydrocarbon solvents immediately priorto a polymerization reactor it is desirable that the combination yield anew polymerization catalyst in less than 1 h, less than 30 min, or lessthan 15 min. Shorter times are more effective, as the new catalyst isready before being introduces into the reactor, providing the potentialfor faster flow rates.

In another embodiment, an aluminum alkyl, an ethoxylated aluminum alkyl,an aluminoxane, an anti-static agent or a borate activator, such as a C1to C15 alkyl aluminum (for example tri-isobutyl aluminum, trimethylaluminum or the like), a C1 to C15 ethoxylated alkyl aluminum or methylaluminoxane, ethyl aluminoxane, isobutylaluminoxane, modifiedaluminoxane or the like are added to the mixture of the slurry and thesolution in line. The alkyls, antistatic agents, borate activatorsand/or aluminoxanes may be added from an alkyl vessel 210 directly tothe combination of the solution and the slurry, or may be added via anadditional alkane (such as isopentane, hexane, heptane, and or octane)carrier stream, for example, from a hydrocarbon vessel 212. Theadditional alkyls, antistatic agents, borate activators and/oraluminoxanes may be present at up to about 500 ppm, at about 1 to about300 ppm, at 10 to about 300 ppm, or at about 10 to about 100 ppm.Carrier streams that may be used include isopentane and or hexane, amongothers. The carrier may be added to the mixture of the slurry and thesolution, typically at a rate of about 0.5 to about 60 lbs/hr (27kg/hr).

Likewise a carrier gas 214, such as nitrogen, argon, ethane, propane,and the like, may be added in-line to the mixture of the slurry and thesolution. Typically the carrier gas may be added at the rate of about 1to about 100 lb/hr (0.4 to 45 kg/hr), or about 1 to about 50 lb/hr (5 to23 kg/hr), or about 1 to about 25 lb/hr (0.4 to 11 kg/hr).

In another embodiment, a liquid carrier stream is introduced into thecombination of the solution and slurry that is moving in a downwarddirection. The mixture of the solution, the slurry and the liquidcarrier stream may pass through a mixer or length of tube for mixingbefore being contacted with a gaseous carrier stream.

Similarly, a comonomer 216, such as hexene, another alpha-olefin, ordiolefin, may be added in-line to the mixture of the slurry and thesolution. The slurry/solution mixture is then passed through aninjection tube 220 to a reactor 222. In some embodiments, the injectiontube may aerosolize the slurry/solution mixture. Any number of suitabletubing sizes and configurations may be used to aerosolize and/or injectthe slurry/solution mixture.

In one embodiment, a gas stream 226, such as cycle gas, or re-cycle gas224, monomer, nitrogen, or other materials is introduced into a supporttube 228 that surrounds the injection tube 220. To assist in properformation of particles in the reactor 222, a nucleating agent 218, suchas fumed silica, can be added directly into the reactor 222.

When a metallocene catalyst or other similar catalyst is used in the gasphase reactor, oxygen or fluorobenzene can be added to the reactor 222directly or to the gas stream 226 to control the polymerization rate.Thus, when a metallocene catalyst (which is sensitive to oxygen orfluorobenzene) is used in combination with another catalyst (that is notsensitive to oxygen) in a gas phase reactor, oxygen can be used tomodify the metallocene polymerization rate relative to thepolymerization rate of the other catalyst. An example of such a catalystcombination is bis(n-propyl cyclopentadienyl)zirconium dichloride and[(2,4,6-Me3C6H2)NCH2 CH2]2NHZrBn2, where Me is methyl orbis(indenyl)zirconium dichloride and [(2,4,6-Me3C6H2)NCH2CH2]2NHHfBn2,where Me is methyl. For example, if the oxygen concentration in thenitrogen feed is altered from 0.1 ppm to 0.5 ppm, significantly lesspolymer from the bisindenyl ZrCl2 will be produced and the relativeamount of polymer produced from the [(2,4,6-Me3C6H2)NCH2CH2]2NHHfBn2 isincreased. WO 1996/009328 discloses the addition of water or carbondioxide to gas phase polymerization reactors, for example, for similarpurposes. In one embodiment, the contact temperature of the slurry andthe solution is in the range of from 0° C. to about 80° C., from about0° C. to about 60° C., from about 10° C., to about 50° C., and fromabout 20° C. to about 40° C.

The example above is not limiting, as additional solutions and slurriesmay be included. For example, a slurry can be combined with two or moresolutions having the same or different catalyst compounds and oractivators. Likewise, the solution may be combined with two or moreslurries each having the same or different supports, and the same ordifferent catalyst compounds and or activators. Similarly, two or moreslurries combined with two or more solutions, preferably in-line, wherethe slurries each comprise the same or different supports and maycomprise the same or different catalyst compounds and or activators andthe solutions comprise the same or different catalyst compounds and oractivators. For example, the slurry may contain a supported activatorand two different catalyst compounds, and two solutions, each containingone of the catalysts in the slurry, are each independently combined,in-line, with the slurry.

Use of Catalyst Composition to Control Product Properties

The properties of the product polymer may be controlled by adjusting thetiming, temperature, concentrations, and sequence of the mixing of thesolution, the slurry and any optional added materials (nucleatingagents, catalyst compounds, activators, etc) described above. The MWD,MI, density, MFR, relative amount of polymer produced by each catalyst,and other properties of the polymer produced may also be changed bymanipulating process parameters. Any number of process parameters may beadjusted, including manipulating hydrogen concentration in thepolymerization system, changing the amount of the first catalyst in thepolymerization system, changing the amount of the second catalyst in thepolymerization system. Other process parameters that can be adjustedinclude changing the relative ratio of the catalyst in thepolymerization process (and optionally adjusting their individual feedrates to maintain a steady or constant polymer production rate). Theconcentrations of reactants in the reactor 222 can be adjusted bychanging the amount of liquid or gas that is withdrawn or purged fromthe process, changing the amount and/or composition of a recoveredliquid and/or recovered gas returned to the polymerization process,wherein the recovered liquid or recovered gas can be recovered frompolymer discharged from the polymerization process. Further processparameters including concentration parameters that can be adjustedinclude changing the polymerization temperature, changing the ethylenepartial pressure in the polymerization process, changing the ethylene tocomonomer ratio in the polymerization process, changing the activator totransition metal ratio in the activation sequence. Time dependentparameters may be adjusted, such as changing the relative feed rates ofthe slurry or solution, changing the mixing time, the temperature and ordegree of mixing of the slurry and the solution in-line, addingdifferent types of activator compounds to the polymerization process,and adding oxygen or fluorobenzene or other catalyst poison to thepolymerization process. Any combinations of these adjustments may beused to control the properties of the final polymer product.

In one embodiment, the MWD of the polymer product is measured at regularintervals and one of the above process parameters, such as temperature,catalyst compound feed rate, the ratios of the two or more catalysts toeach other, the ratio of comonomer to monomer, the monomer partialpressure, and or hydrogen concentration, is altered to bring thecomposition to the desired level, if necessary. The MWD may be measuredby size exclusion chromatography (SEC), e.g., gel permeationchromatography (GPC), among other techniques.

In one embodiment, a polymer product property is measured in-line and inresponse the ratio of the catalysts being combined is altered. In oneembodiment, the molar ratio of the catalyst compound in the catalystcomponent slurry to the catalyst compound in the catalyst componentsolution, after the slurry and solution have been mixed to form thefinal catalyst composition, is 500:1 to 1:500, or 100:1 to 1:100, or50:1 to 1:50 or 40:1 to 1:10. In another embodiment, the molar ratio ofa Group 15 catalyst compound in the slurry to a ligand metallocenecatalyst compound in the solution, after the slurry and solution havebeen mixed to form the catalyst composition, is 500:1, 100:1, 50:1,10:1, or 5:1. The product property measured can include the dynamicshear viscosity, flow index, melt index, density, MWD, comonomercontent, and combinations thereof. In another embodiment, when the ratioof the catalyst compounds is altered, the introduction rate of thecatalyst composition to the reactor, or other process parameters, isaltered to maintain a desired production rate.

Polymerization Process

The catalyst system can be used to polymerize one or more olefins toprovide one or more polymer products therefrom. Any suitablepolymerization process can be used, including, but not limited to, highpressure, solution, slurry, and/or gas phase polymerization processes.In embodiments that use other techniques besides gas phasepolymerization, modifications to a catalyst addition system that aresimilar to those discussed with respect to FIG. 2 can be used. Forexample, a trim system may be used to feed catalyst to a loop slurryreactor for polyethylene copolymer production.

The terms “polyethylene” and “polyethylene copolymer” refer to a polymerhaving at least 50 wt. % ethylene-derived units. In various embodiments,the polyethylene can have at least 70 wt. % ethylene-derived units, atleast 80 wt. % ethylene-derived units, at least 90 wt. %ethylene-derived units, or at least 95 wt. % ethylene-derived units. Thepolyethylene polymers described herein are generally copolymer, but mayalso include terpolymers, having one or more other monomeric units. Asdescribed herein, a polyethylene can include, for example, at least oneor more other olefins or comonomers. Suitable comonomers can contain 3to 16 carbon atoms, from 3 to 12 carbon atoms, from 4 to 10 carbonatoms, and from 4 to 8 carbon atoms. Examples of comonomers include, butare not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene,1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene, andthe like.

Referring again to FIG. 2, the fluidized bed reactor 222 can include areaction zone 232 and a velocity reduction zone 234. The reaction zone232 can include a bed 236 that includes growing polymer particles,formed polymer particles and a minor amount of catalyst particlesfluidized by the continuous flow of the gaseous monomer and diluent toremove heat of polymerization through the reaction zone. Optionally,some of the re-circulated gases 224 can be cooled and compressed to formliquids that increase the heat removal capacity of the circulating gasstream when readmitted to the reaction zone. A suitable rate of gas flowcan be readily determined by experimentation. Make-up of gaseous monomerto the circulating gas stream can be at a rate equal to the rate atwhich particulate polymer product and monomer associated therewith iswithdrawn from the reactor and the composition of the gas passingthrough the reactor can be adjusted to maintain an essentially steadystate gaseous composition within the reaction zone. The gas leaving thereaction zone 232 can be passed to the velocity reduction zone 234 whereentrained particles are removed, for example, by slowing and fallingback to the reaction zone 232. If desired, finer entrained particles anddust can be removed in a separation system 238, such as a cyclone and/orfines filter. The gas 224 can be passed through a heat exchanger 240where at least a portion of the heat of polymerization can be removed.The gas can then be compressed in a compressor 242 and returned to thereaction zone 232. Additional reactor details and means for operatingthe reactor 222 are described in, for example, U.S. Pat. Nos. 3,709,853;4,003,712; 4,011,382; 4,302,566; 4,543,399; 4,882,400; 5,352,749; and5,541,270; EP 0802202; and Belgian Patent No. 839,380.

The reactor temperature of the fluid bed process can be greater thanabout 30° C., about 40° C., about 50° C., about 90° C., about 100° C.,about 110° C., about 120° C., about 150° C., or higher. In general, thereactor temperature is operated at the highest feasible temperaturetaking into account the sintering temperature of the polymer productwithin the reactor. Thus, the upper temperature limit in one embodimentis the melting temperature of the polyethylene copolymer produced in thereactor. However, higher temperatures may result in narrower MWDs, whichcan be improved by the addition of structure (IV), or otherco-catalysts, as described herein.

Hydrogen gas can be used in olefin polymerization to control the finalproperties of the polyolefin, such as described in the “PolypropyleneHandbook,” at pages 76-78 (Hanser Publishers, 1996). Using certaincatalyst systems, increasing concentrations (partial pressures) ofhydrogen can increase a flow index such as MI of the polyethylenecopolymer generated. The MI can thus be influenced by the hydrogenconcentration. The amount of hydrogen in the polymerization can beexpressed as a mole ratio relative to the total polymerizable monomer,for example, ethylene, or a blend of ethylene and hexene or propylene.

The amount of hydrogen used in the polymerization process can be anamount necessary to achieve the desired MI of the final polyolefinpolymer. For example, the mole ratio of hydrogen to total monomer(H2:monomer) can be greater than about 0.0001, greater than about0.0005, or greater than about 0.001. Further, the mole ratio of hydrogento total monomer (H2:monomer) can be less than about 10, less than about5, less than about 3, and less than about 0.10. A desirable range forthe mole ratio of hydrogen to monomer can include any combination of anyupper mole ratio limit with any lower mole ratio limit described herein.Expressed another way, the amount of hydrogen in the reactor at any timecan range to up to about 5,000 ppm, up to about 4,000 ppm in anotherembodiment, up to about 3,000 ppm, or between about 50 ppm and 5,000ppm, or between about 50 ppm and 2,000 ppm in another embodiment. Theamount of hydrogen in the reactor can range from a low of about 1 ppm,about 50 ppm, or about 100 ppm to a high of about 400 ppm, about 800ppm, about 1,000 ppm, about 1,500 ppm, or about 2,000 ppm, based onweight. Further, the ratio of hydrogen to total monomer (H2:monomer) canbe about 0.00001:1 to about 2:1, about 0.005:1 to about 1.5:1, or about0.0001:1 to about 1:1. The one or more reactor pressures in a gas phaseprocess (either single stage or two or more stages) can vary from 690kPa (100 psig) to 3,448 kPa (500 psig), in the range from 1,379 kPa (200psig) to 2,759 kPa (400 psig), or in the range from 1,724 kPa (250 psig)to 2,414 kPa (350 psig).

The gas phase reactor can be capable of producing from about 10 kg ofpolymer per hour (25 lbs/hr) to about 90,900 kg/hr (200,000 lbs/hr), orgreater, and greater than about 455 kg/hr (1,000 lbs/hr), greater thanabout 4,540 kg/hr (10,000 lbs/hr), greater than about 11,300 kg/hr(25,000 lbs/hr), greater than about 15,900 kg/hr (35,000 lbs/hr), andgreater than about 22,700 kg/hr (50,000 lbs/hr), and from about 29,000kg/hr (65,000 lbs/hr) to about 45,500 kg/hr (100,000 lbs/hr).

As noted, a slurry polymerization process can also be used inembodiments. A slurry polymerization process generally uses pressures inthe range of from about 101 kPa (1 atmosphere) to about 5,070 kPa (50atmospheres) or greater, and temperatures in the range of from about 0°C. to about 120° C., and more particularly from about 30° C. to about100° C. In a slurry polymerization, a suspension of solid, particulatepolymer can be formed in a liquid polymerization diluent medium to whichethylene, comonomers, and hydrogen along with catalyst can be added. Thesuspension including diluent can be intermittently or continuouslyremoved from the reactor where the volatile components are separatedfrom the polymer and recycled, optionally after a distillation, to thereactor. The liquid diluent employed in the polymerization medium can bean alkane having from 3 to 7 carbon atoms, such as, for example, abranched alkane. The medium employed should be liquid under theconditions of polymerization and relatively inert. When a propane mediumis used the process should be operated above the reaction diluentcritical temperature and pressure. In one embodiment, a hexane,isopentane, or isobutane medium can be employed. The slurry can becirculated in a continuous loop system.

A number of tests can be used to compare resins from different sources,catalyst systems, and manufacturers. Such tests can include melt index,high load melt index, melt index ratio, density, dies swell,environmental stress crack resistance, and many others. Results of testsruns on resins made in embodiments described herein are presented in theexamples section.

The product polyethylene can have a melt index ratio (MIR or I21/I2)ranging from about 10 to less than about 300, or, in many embodiments,from about 15 to about 150. Flow index (FI, HLMI, or I21 can be measuredin accordance with ASTM D1238 (190° C., 21.6 kg). The melt index (MI,I2) can be measured in accordance with ASTM D1238 (at 190° C., 2.16 kgweight).

Density can be determined in accordance with ASTM D-792. Density isexpressed as grams per cubic centimeter (g/cm3) unless otherwise noted.The polyethylene can have a density ranging from a low of about 0.89g/cm3, about 0.90 g/cm3, or about 0.91 g/cm3 to a high of about 0.95g/cm3, about 0.96 g/cm3, or about 0.97 g/cm3. The polyethylene can havea bulk density, measured in accordance with ASTM D1895 method B, of fromabout 0.25 g/cm3 to about 0.5 g/cm3. For example, the bulk density ofthe polyethylene can range from a low of about 0.30 g/cm3, about 0.32g/cm3, or about 0.33 g/cm3 to a high of about 0.40 g/cm3, about 0.44g/cm3, or about 0.48 g/cm3.

The polyethylene can be suitable for such articles as films, fibers,nonwoven and/or woven fabrics, extruded articles, and/or moldedarticles. Examples of films include blown or cast films formed in singlelayer extrusion, coextrusion, or lamination useful as shrink film, clingfilm, stretch film, sealing films, oriented films, snack packaging,heavy duty bags, grocery sacks, baked and frozen food packaging, medicalpackaging, industrial liners, membranes, etc. in food-contact andnon-food contact applications, agricultural films and sheets. Examplesof fibers include melt spinning, solution spinning and melt blown fiberoperations for use in woven or non-woven form to make filters, diaperfabrics, hygiene products, medical garments, geotextiles, etc. Examplesof extruded articles include tubing, medical tubing, wire and cablecoatings, pipe, geomembranes, and pond liners. Examples of moldedarticles include single and multi-layered constructions by injectionmolding or rotation molding or blow molding processes in the form ofbottles, tanks, large hollow articles, rigid food containers and toys,etc.

Data for example BOCD polymers are presented in Tables 1b, 2a, and 2b.Data for selected comparative conventional polymers are given in Table2c. These tables are discussed in more detail throughout the discussionbelow.

Table 1b is a summary of production and property data with respect toexample BOCD polymers. Table 1b data as generated may be representativeof a technique in which a target or desired different MFR's for variouspolymers are selected or specified. (See also FIGS. 5A, 5B, and 6 forexemplary graphical representations of such a technique.) To achieve theselected target MFR for a given polymer, the polymerization reactortemperature and an amount of a second (trim) catalyst to feed to thereactor the reactor are adjusted or specified. To maintain the same orsimilar density and MI through the range of MFR's for the variouspolymers, the comonomer amount or ratio to monomer (e.g.,1-hexene/ethylene or butene/ethylene) and the hydrogen amount or ratioto monomer (e.g., hydrogen/ethylene) in the reactor feed or in thepolymerization mixture in the reactor may be adjusted (selected orspecified).

For instance, polymer A0 was produced at a reactor temperature of 86° C.and with no second or trim catalyst to give a polymer MFR of 21. Thesimilar polymer A0-R was reproduced. Then, polymer A1 produced at thesame reactor temperature of 86° C. but with the addition of a second ortime catalyst to give a higher MFR of 29. To maintain the density and MIsubstantially the same, respectively, the 1-hexene/ethylene andhydrogen/ethylene ratios are adjusted. Such a technique may be repeatedthrough a range of MFRs, as indicated in Table 1b. It should be notedfor some of the polymers, the reactor temperature is lower from 86° C.to 80° C. to give an increased MFR of the polymer. Moreover, anadjustment may be to change to comonomer type, such as changing from1-hexene to butene. Of course, other adjustments with respect tooperating variables and materials may be made for a variety of MFRtargets over desired density and MI. Lastly, Table 1b demonstrates thatMFR may be “decoupled” from MI.

TABLE 1b Summary Independent Control of MI/MFR Product BTEC BTEC BTECRxtr Tmp C2 P-P Trim C6/C2 C4/C2 H2/C2 Description Density MI(I2) MFR(I21/12) (Deg C.) (psia) (Calc Flow g/hr) (mol ratio) (ratio) (PPM/Mol%) Coreset A0 0.918 1.1 21 86 220 0.0140 7.00 A0-R 0.919 1.0 22 86 2200.0140 7.00 A1 0.920 0.9 29 86 220 61.7 0.0167 7.50 A2 0.922 0.9 36 86220 99.6 0.0190 7.93 B0 0.919 1.1 27 80 220 0.0152 7.11 B1 0.919 0.9 3780 220 40.1 0.0172 7.10 B2 0.922 0.9 59 80 220 72.9 0.0192 6.87 Branchedout from coreset for different MI/Density/Comonomer Type A1-b 0.917 0.826 86 220 44.0 0.0183 7.35 A1-c 0.927 0.8 26 86 220 58.1 0.0130 4.70A2-b 0.920 1.0 37 86 220 111.5 0.0727 8.54 B1-b 0.919 0.7 37 80 220 43.00.0175 7.00 B1-c 0.925 0.9 36 80 220 49.9 0.0152 5.03 B1-d 0.921 0.8 3880 220 125.0 0.0600 7.70 B2-b-A 0.930 0.5 41 80 220 129.1 0.0161 3.20B2-b-B 0.932 0.6 50 80 220 298.9 0.0190 3.21

TABLE 2a Summary of Cryo-CFC Analysis with Equal Halves for Core-setCoreset Sample ID A0 A0-R A1 A2 B0 B1 B2 Density (g/cm3) 0.918 0.9190.920 0.922 0.919 0.919 0.922 I-2 (dg/min) 1.1 1.0 0.9 0.9 1.1 0.9 0.9MFR (I-21/I-2) 21 22 29 36 27 37 59 (log(Mw1) − log(Mw2))/(Tw1 − Tw2)−0.0166 −0.0189 −0.0190 −0.0196 −0.0191 −0.0203 −0.0222 Mw1/Mw2 2.042.17 2.74 3.27 2.94 3.73 4.53 Tw1 − Tw2 (° C.) −18.7 −17.8 −23.1 −26.3−24.5 −28.2 −29.6

TABLE 2b Summary of Cryo-CFC Analysis with Equal Halves for Branched-outBranched out from corset Sample ID A1-b A1-c A2-b B1-b B1-c B1-d B2-b-AB2-b-B Density (g/cm3) 0.917 0.927 0.920 0.919 0.925 0.921 0.930 0.932I-2 (dg/min) 0.8 0.8 1.0 0.7 0.9 0.8 0.5 0.6 MFR (I-21/I-2) 26 26 37 3736 38 41 50 (log(Mw1) − log(Mw2))/(Tw1 − Tw2) −0.0165 −0.0219 −0.0188−0.0205 −0.0230 −0.0190 −0.0264 −0.0279 Mw1/Mw2 2.62 2.47 3.88 3.85 3.233.65 3.51 3.32 Tw1 − Tw2 (° C.) −25.3 −18.0 −31.4 −28.6 −22.2 −29.6−20.7 −18.7

TABLE 2c Summary of Cryo-CFC Analysis with Equal Halves for ComparativeSamples Exceed Exceed Enable Enable 1018CA 1327CA 2010CH 2705CHLL3201.69 LD071.LR Density (g/cm3) 0.919 0.928 0.920 0.928 0.927 0.924I-2 (dg/min) 1.0 1.3 0.9 0.5 0.9 0.7 MFR (I-21/I-2) 15 15 32 45 25 65(log(Mw1) − log(Mw2))/(Tw1 − Tw2) −0.0049 −0.0032 0.0224 0.0212 0.01140.0392 Mw1/Mw2 1.14 1.07 0.78 0.87 0.53 0.36 Tw1 − Tw2 (° C.) −11.4 −9.1−4.9 −2.8 −24.1 −11.3

Measuring Tw1, Tw2, Mw1 & Mw2 from CFC

A new technique has been developed for determining both MWD and SCBDcompositional information, using cross fractionation (CFC), to compareexperimental polymers to competitive products on the market. The valuesTw1, Tw2, Mw1 & Mw2 may be derived from the CFC data file as reportedfrom the instrument software. In the section of “Fraction summary” inthe CFC data file, each fraction is listed by its fractionationtemperature (Ti) along with its normalized wt. % value (Wi), cumulativewt. %, i.e., Sum wt. and various moments of molecular weight averages(including Mwi).

FIGS. 3A and 3B are plots that graphically represent calculations usedto determine the CFC result. Fractions having MWD data are considered.In both FIGS. 3A and 3B, the x-axis 302 is the elution temperature incentigrade, while the right hand y-axis 304 is the value of the integral306 of the molecular weights eluted. The temperature 308 at which 100%of the material has eluted in this example is about 100° C. The point atwhich 50% of the polymer has eluted is determined by the integral 306,which is used to divide each of the plots into a lower half 310 and anupper half 312.

The values Tw1, Tw2, Mw1 & Mw2 in FIGS. 3A and 3B are derived from theCFC data file as reported from the instrument software. In the sectionof “Fraction summary” in the CFC data file, each fraction is listed byits fractionation temperature (T_(i)) along with its normalized wt. %value (W_(i)), cumulative wt. %, i.e., Sum wt. on FIGS. 3A and 3B, andvarious moments of molecular weight averages (including Mw_(i)).

To calculate values of Tw1, Tw2, Mw1 & Mw2, the data in “Fractionsummary” was divided into two roughly equal halves. Weight averages ofT_(i) and Mw_(i) for each half were calculated according to theconventional definition of weight average. Fractions which did not havesufficient quantity (i.e., <0.5 wt. %) to be processed for molecularweight averages in the original data file were excluded from thecalculation of Tw1, Tw2, Mw1 & Mw2.

The first part of the process is illustrated by FIG. 3A. From thesection of fraction summary in the CFC data file, the fraction whosecumulative wt.% (i.e., Sum wt) is closest to 50 is identified (e.g., thefraction at 84° C. on FIG. 3A). The Fraction summary data is dividedinto two halves, e.g., Ti<=84° C. as the 1^(st) half and Ti>84° C. asthe 2^(nd) half on FIG. 3A. Fractions which do not have molecular weightaverages reported in the original data file are excluded, e.g.,excluding the fractions with Ti between 25° C. and 40° C. on FIG. 3A.

In FIG. 3A, the left hand y-axis 310 represents the wt % 312 of theeluted fraction. Using the procedure above to divide the curves into twohalves, these values are used to calculate the weight average elutiontemperature for each half using the formula shown in Eqn. 1.

$\begin{matrix}{{Tw} = \frac{{\sum\; {T_{i}W_{i}}}\mspace{11mu}}{\sum\; W_{i}}} & {{Eqn}.\mspace{14mu} 1}\end{matrix}$

In Eqn. 1, Ti represents the elution temperature for each elutedfraction, and Wi represents the normalized weight % (polymer amount) ofeach eluted fraction. For the example shown in FIG. 3A, this provides aweight average elution temperature of 64.0° C. for the first half, and91.7° C. for the second half.

In FIG. 3B, the left hand axis 618 represents the weight averagemolecular weight (Mw_(i)) 320 of each eluted fraction. These values areused to calculate the weight average molecular weight for each halfusing the formula shown in Eqn. 2.

$\begin{matrix}{{Mw} = \frac{\sum\; {{Mw}_{i}W_{i}}}{\sum\; W_{i}}} & {{Eqn}.\mspace{14mu} 2}\end{matrix}$

In Eqn. 2, Mw_(i) represents the weight average molecular weight of eacheluted fraction, and W_(i) represents the normalized weight % (polymeramount) of each eluted fraction. For the example shown in FIG. 3B, thisprovides a weight average molecular weight of about 238,000 for thefirst half, and about 74,000 for the second half. The values calculatedusing the techniques described above may be used to classify theMWD×SCBD for BOCD polymers (Tables 2a and 2b) and control polymers(Table 3) as shown in FIG. 4.

FIG. 4 is a semi-log plot 400 of (Mw1/Mw2) vs. (Tw1−Tw2), depicting aregion 406 for the polymers listed in Tables 2a and 2b. In the plot 400,the x-axis 402 represents the value of the difference between the firstand second weight average elution temperatures. The y-axis 404 in a logscale represents the ratio of the first weight average molecular weightto the second weight average molecular weight. Each of the polymers inTables 2a and 2b, which also list the calculated values for the weightaverage molecular weights and the weight average elution temperatures,are represented as falling in region 406. In this illustratedembodiment, the region 406 has a lower bound of −15° C. for Tw1−Tw2, anda lower bound of 2.0 for Mw1/Mw2.

Polymers that fall in the region 406 may have a broad, orthogonalcomposition distribution. A BOCD indicates that lower molecular weightpolymer chains in the polymer have a high density, e.g., due to a lackof short chain branching (SCB), while higher molecular weight segmentshave a low density, e.g. due to higher amounts of SCB. In contrast,conventional polymers (e.g., ZN-LLDPE) falling outside of region 406 maygenerally have longer polymer chains that have a higher density thanshorter polymer chains. Such conventional polymers may generally resideon the lower portion of the plot 400.

As can be seen, the newer polymers (Tables 2a, 2b) fall in the region706 indicating a different MWD and SCBD as compared to the commercialpolymers falling outside of region 406. Thus, the use of the techniquedescribed above can identify polymers that have BOCDs. Accordingly, thetechnique can be use both to screen new polymers for the distributionand to control polymer production to target particular locations in theregion 706.

Testing Procedure with Cross-fractionation chromatography (CFC)

In examples, cross-fractionation chromatography (CFC) was performed on aCFC-2 instrument from Polymer Char, Valencia, Spain. The instrument wasoperated and subsequent data processing, e.g., smoothing parameters,setting baselines, and defining integration limits, performed accordingto the manner described in the CFC User Manual provided with theinstrument or in a manner commonly used in the art. The instrument wasequipped with a TREF column (stainless steel; o.d., ⅜″; length, 15 cm;packing, non-porous stainless steel micro-balls) in the first dimensionand a GPC column set (3×PLgel 10 μm Mixed B column from Polymer Labs,UK) in the second dimension. Downstream from the GPC column was aninfrared detector (IR4 from Polymer Char) capable of generating anabsorbance signal that is proportional to the concentration of polymerin solution.

The sample to be analyzed was dissolved in ortho-dichlorobenzene, at aconcentration of about 5 mg/ml, by stirring at 150° C. for 75 min. Thena 0.5-ml volume of the solution containing 2.5 mg of polymer was loadedin the center of the TREF column and the column temperature was reducedand stabilized at ≈120° C. for 30 min. The column was then cooled slowly(0.2° C./min) to 30° C. (for ambient runs) or −15° C. (for cryogenicruns) to crystallize the polymer on the inert support. The lowtemperature was held for 10 min before injecting the soluble fractioninto the GPC column. All GPC analyses were done using solventortho-dichlorobenzene at 1 ml/min, a column temperature of 140° C., andin the “Overlap GPC Injections” mode. Then the subsequenthigher-temperature fractions were analyzed by increasing the TREF columntemperature to the fraction set-points in a stepwise manner, letting thepolymer dissolve for 16 min (“Analysis Time”), and injecting thedissolved polymer into the GPC column for 3 min (“Elution Time”).

The universal calibration method was used for determining the molecularmass of eluting polymers. Thirteen narrow molecular-weight distributionpolystyrene standards (obtained from Polymer Labs, UK) within the rangeof 1.5-8200 Kg/mol were used to generate a universal calibration curve.Mark-Houwink parameters were obtained from Appendix I of “Size ExclusionChromatography” by S. Mori and H. G. Barth (Springer). For polystyreneK=1.38×10−4 dl/g and α=0.7; and for polyethylene K=5.05×10−4 dl/g andα=0.693 were used. Fractions having a weight % recovery (as reported bythe instrument software) of less than 0.5% were not processed forcalculations of molecular-weight averages (Mn, Mw, etc.) of theindividual fractions or of aggregates of fractions.

Blown film evaluation data are presented in Tables 3a, 3b, 3c, and 3d.Tables 3a and 3b each compare BOCD polymers A0, A1, and B0 versusconventional polymer Exceed 1018 at low MFR. Tables 3c and 3d eachcompare BOCD polymers A2, B1, and B2 versus conventional polymer Enable1020 at high MFR.

TABLE 3a Blown Film Evaluation of Core-set vs. Exceed at low MFR (1 milGauge) Exceed 1018 CA @ 1 mil A0 @ 1 mil A1 @ 1 mil B0 @ 1 mil Density(g/cm3) 0.919 0.918 0.920 0.919 MI (I-2) (dg/min) 1.0 1.1 0.9 1.1 MFR(I-21/I-2) 15 21 29 27 Motor Load (%) 64.9 60.4 54.6 52.9 E.S.O.(lb/HP-hr) 9.26 10.41 10.77 11.45 MD Modulus (psi) 24,625 27,302 30,88327,360 TD Modulus (psi) 27,167 33,362 40,048 32,126 26″ Dart (g/mil) 342530 702 649 Average Mode (psi) 25,896 30,332 35,466 29,743 Cal Dart per.(g/mil) 488 294 193 312 U.S. Pat. No. 6,255,426 (% dif) 70% 180% 364%208% Msrd. Dart vs. U.S. Pat. No. 6,255,426

TABLE 3b Blown Film Evaluation of Core-set vs. Exceed at low MFR (2 milgauge) Exceed 1018 CA @ 2 mil A0 @ 2 mil A1 @ 2 mil B0 @ 2 mil Density(g/cm3) 0.919 0.918 0.920 0.919 MI (I-2) (dg/min) 1.0 1.1 0.9 1.1 MFR(I-21/I-2) 15 21 29 27 Motor Load (%) 65.1 60.7 54.1 53.0 E.S.O.(lb/HP-hr) 9.20 10.49 10.83 11.36 MD Modulus (psi) 25,755 28,220 31,61430,900 TD Modulus (psi) 28,183 35,834 39,665 33,534 26″ Dart (g/mil)622 >655 >667 >664 Average Mode (psi) 26,969 32,027 35,640 32,217 CalDart per. (g/mil) 426 251 191 247 U.S. Pat. No. 6,255,426 (% dif) 146%279% 367% 283% Msrd. Dart vs. U.S. Pat. No. 6,255,426

TABLE 3c Blown Film Evaluation of Core-set vs. Enable at high MFR (1 milgauge) Enable 2010 CH @ 1 mil A2 @ 1 mil B1 @ 1 mil B2 @ 1 mil Density(g/cm3) 0.920 0.922 0.919 0.922 MI (I-2) (dg/min) 0.9 0.9 0.9 0.9 MFR(I-21/I-2) 32 36 37 59 Motor Load (%) 50.8 49.4 50.8 45.1 E.S.O.(lb/HP-hr) 11.75 11.49 11.23 12.34 MD Modulus (psi) 27,410 35,212 33,63633,945 TD Modulus (psi) 32,178 46,169 35,444 49,647 26″ Dart (g/mil) 185725 906 533 Average Mode (psi) 29,794 40,691 34,540 41,796 Cal Dart per.(g/mil) 310 146 206 140 U.S. Pat. No. 6,255,426 (% dif) 60% 495% 440%380% Msrd. Dart vs. U.S. Pat. No. 6,255,426

TABLE 3d Blown Film Evaluation of Core-set vs. Enable at high MFR (2 milgauge) Enable 2010 CH @ 2 mil A2 @ 2 mil B1 @ 2 mil B2 @ 2 mil Density(g/cm3) 0.920 0.922 0.919 0.922 I-2 (dg/min) 0.9 0.9 0.9 0.9 MFR(I-21/I-2) 32 36 37 59 Motor Load (%) 50.8 49.5 50.8 E.S.O. (lb/HP-hr)11.91 11.48 11.27 MD Modulus (psi) 27,395 30,876 30,490 TD Modulus (psi)30,049 41,384 38,703 26″ Dart (g/mil) 258 587 >645 Average Mode (psi)28,722 36,130 34,597 Cal Dart per. (g/mil) 348 185 205 U.S. Pat. No.6,255,426 (% dif) 74% 317% 342% Msrd. Dart vs. U.S. Pat. No. 6,255,426

FIG. 5A is a diagrammatical representation of techniques for generatingtargets or recipes, and producing, some of the exemplary BOCD polymersof Table 1, those listed in Table 2a. The techniques may be to producevarious BOCD polymers over a range of polymer MFRs at the same orsimilar respective polymer density and MI. Such techniques may rangefrom a design of experiments (DOE) for target values of polymerizationoperating variables and polymer properties, to the control of actualcommercial production of the BOCD polymers. In the illustratedembodiment of FIG. 5A, a target MFR range 502 of 15-22 is specified witha chosen reactor temperature (e.g., at 86° C. in Table 1). This is basedon the learning from prior experiments for the MFR capability of asingle catalyst at various reactor temperatures. As indicated in block504, the single catalyst system (HfP) in this example is specified withinitial polymerization reactor conditions for the target MFR range 502.Adjustments 506 are made to operating variable targets to give polymerA0 508. As indicated above with respect to Table 1, the reactortemperature and amount of any second or trim catalyst may be primaryvariables for MFR. The comonomer/ethylene ratio, e.g., 1-hexene/ethylene(C6/C2) ratio or butane/ethylene (C4/C2) ratio, may be a primaryvariable for polymer density. The hydrogen/ethylene (H2/C2) ratio may bea primary variable for polymer MI.

Continuing with FIG. 5A, for a target polymer MFR range 510 of 26-30, asecond catalyst (i.e., Et-Ind) is added to the system at the conditionof 508 until the MFR target specified by block 512 is reached while MIand density were allowed to float during the transition. After the MFRtarget in 512 is achieved, operation adjustments 514 are made to givepolymer A1 516 with MI & Density target same as 508. Operatingadjustments 518 are made to give polymer A1-b 520. Operating adjustments522 are made to give polymer A1-c 524. With such operation adjustments,one can independently change MI and Density for 516, 520 & 254 whilemaintaining the MFR in a very tight range of 510. For a target polymerMFR range 526 in the mid-30's, a dual-catalyst system (HfP and Et-Ind)and initial reactor conditions are specified, as reference by block 528.Operating adjustments 530 are made to give polymer A2 532. Operatingadjustments 534 are made to give polymer A2-b 536. As discussed, theadjustments 514, 518, 522, 530, and 534 are indicated in Table 1b above.

FIG. 5B is similar to FIG. 5A but with different BOCD polymers fromTable 1b. FIG. 5B is a diagrammatical representation of techniques forgenerating targets or recipes, and producing, some of the exemplary BOCDpolymers of Table 1b, those listed in Table 2b. Again, such techniqueswith respect to FIGS. 5A and 5B may be to produce various BOCD polymersover a range of polymer MFRs while maintaining the polymer density andMI. As mentioned, the techniques may range from DOE for target values ofpolymerization operating variables (e.g., in recipes) and polymerproperties, to the control of actual commercial production of the BOCDpolymers, and so forth. In the illustrated embodiment of FIG. 5B, at adifferent chosen reactor temperature (e.g., 80° C. in Table 1b), adifferent target MFR range 510 of 26-30 is specified for the same singlecatalyst. As indicated in block 540, the single catalyst system (HfP) inthis example is specified with initial polymerization reactor conditionsfor the target MFR range 510. Adjustments 540 are made to operatingvariables or operating variable targets to give polymer B0 544. For atarget polymer MFR range 526 of mid-30's, a similar procedure as in FIG.5A from 508 to 512 is followed to reach 546 from 544 of FIG. 5B.Operating adjustments 548 are made to give polymer B1 550. Operatingadjustments 552 are made to give polymer B1-b 554. Operating adjustments556 are made to give polymer B1-c 558. Further, operating adjustments560 are made to give polymer B1-d 562. For a target polymer MFR range564 of 35-55, a dual-catalyst system (HfP and Et-Ind) and initialreactor conditions are specified, as referenced by block 566. Operatingadjustments 568 are made to give polymer B2 570. Operating adjustments572 are made to give polymer B2-b 574. The adjustments 540, 548, 552,556, 560, 568, and 572 are indicated in Table 1b above. Again, thereactor temperature and trim catalyst ratio may be primary variables or“knobs” for MFR. The comonomer/ethylene ratio, e.g., C6/C2 or C4/C2, maybe a primary variable or “knob” for polymer density. The H2/C2 ratio maybe a primary variable or “knob” for polymer MI.

FIG. 6 is an exemplary method 600 for producing polyethylene includingpolyethylene having BOCD. The method 600 may involve developing recipetargets for the production of polyethylene, evaluating the production ofpotential BOCD polymer, and/or the actual real-time control in theproduction of polyethylene, and so forth. At block 602, a target MFR ofthe polyethylene polymer is desired or specified. In certainembodiments, the method 600 may involve a range of polymer MFR over thesame MI and same density. The polymerization reactor temperature and thecatalyst trim ratio (if a second catalyst is employed) are specified oradjusted to give the desired polymer MFR, as indicated by blocks 604 and606. At block 608, the amount of hydrogen is specified or adjusted tomaintain polymer MI. The adjustment may be to the hydrogen/ethylene(H2/C2) ratio in the polymerization mixture in the reactor. At block610, the amount of comonomer is specified or adjusted to maintainpolymer density. The adjustment may be to the comonomer/ethylene (e.g.,C6/C2 or C4/C2) ratio in a feed stream to the reactor and/or in thepolymerization mixture in the reactor.

All numerical values are “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art. Further, variousterms have been defined above. To the extent a term used in a claim isnot defined above, it should be given the broadest definition persons inthe pertinent art have given that term as reflected in at least oneprinted publication or issued patent. All patents, test procedures, andother documents cited in this application are fully incorporated byreference to the extent such disclosure is not inconsistent with thisapplication and for all jurisdictions in which such incorporation ispermitted.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention can be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1.-16. (canceled)
 17. A polymer comprising: polyethylene formed: in apolymerization reactor via a polymerization catalyst system comprising afirst catalyst and a second catalyst; and by adjusting operatingconditions of the polymerization reactor and an amount of the secondcatalyst fed to the polymerization reactor to control melt index (MI)and density of the polyethylene based on a target melt flow ratio (MFR)and a desired MWD and CD combination.
 18. The polymer of claim 17,wherein the polyethylene comprises a copolymer of ethylene and an alphaolefin comonomer having from 4 to 20 carbon atoms.
 19. The polymer ofclaim 18, wherein the alpha olefin comonomer comprises 1-hexene.
 20. Thepolymer of claim 17, wherein the polyethylene comprises a bimodalpolyethylene with respect to molecular weight (Mw).
 21. The polymer ofclaim 17, wherein the MI of the polyethylene is in a range from 0.1 to5.0 dg/min. 22.-49. (canceled)